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2,300 | string indexing each character in string has numbered position called an index you can access the character at the nth position by putting the number between two square brackets ([]immediately after the stringflavor "fig pieflavor[ 'iflavor[ returns the character at position in "fig pie"which is wait isn' the first character of "fig pie"in python--and in most other programming languages--counting always starts at zero to get the character at the beginning of stringyou need to access the character at position flavor[ 'fimportant forgetting that counting starts with zero and trying to access the first character in string with the index results in an by-one error off-by-one errors are common source of frustration for beginning and experienced programmers alikethe following figure shows the index for each character of the string "fig pie" |
2,301 | if you try to access an index beyond the end of stringthen python raises an indexerrorflavor[ traceback (most recent call last)file ""line in flavor[ indexerrorstring index out of range the largest index in string is always one less than the string' length since "fig piehas length of seventhe largest index allowed is strings also support negative indicesflavor[- 'ethe last character in string has index - which for "fig pieis the letter the second to last character has index - and so on the following figure shows the negative index for each character in the string "fig pie" - - - - - - - just like with positive indicespython raises an indexerror if you try to access negative index less than the index of the first character in the stringflavor[- traceback (most recent call last)file ""line in flavor[- indexerrorstring index out of range negative indices may not seem useful at firstbut sometimes they're better choice than positive index |
2,302 | for examplesuppose string input by user is assigned to the variable user_input if you need to get the last character of the stringhow do you know what index to useone way to get the last character of string is to calculate the final index using len()final_index len(user_input last_character user_input[final_indexgetting the final character with the index - takes less typing and doesn' require an intermediate step to calculate the final indexlast_character user_input[- string slicing suppose you need string containing just the first three letters of the string "fig pieyou could access each character by index and concatenate them like thisfirst_three_letters flavor[ flavor[ flavor[ first_three_letters 'figif you need more than just the first few letters of stringthen getting each character individually and concatenating them together is clumsy and long-winded fortunatelypython provides way to do this with much less typing you can extract portion of stringcalled substringby inserting colon between two index numbers set inside square brackets like thisflavor "fig pieflavor[ : 'fig |
2,303 | flavor[ : returns the first three characters of the string assigned to flavorstarting with the character at index and going up to but not including the character at index the [ : part of flavor[ : is called slice in this caseit returns slice of "fig pieyumstring slices can be confusing because the substring returned by the slice includes the character whose index is the first number but doesn' include the character whose index is the second number to remember how slicing worksyou can think of string as sequence of square slots the left and right boundaries of each slot are numbered sequentially from zero up to the length of the stringand each slot is filled with character in the string here' what this looks like for the string "fig pie" sofor "fig pie"the slice [ : returns the string "fig"and the slice [ : returns the string pieif you omit the first index in slicethen python assumes you want to start at index flavor[: 'figthe slice [: is equivalent to the slice [ : ]so flavor[: returns the first three characters in the string "fig piesimilarlyif you omit the second index in the slicethen python assumes you want to return the substring that begins with the character |
2,304 | whose index is the first number in the slice and ends with the last character in the stringflavor[ :piefor "fig pie"the slice [ :is equivalent to the slice [ : since the character at index is spaceflavor[ : returns the substring that starts with the space and ends with the last letterpieif you omit both the first and second numbers in sliceyou get string that starts with the character at index and ends with the last character in other wordsomitting both numbers in slice returns the entire stringflavor[:'fig pieit' important to note thatunlike with string indexingpython won' raise an indexerror when you try to slice between boundaries that fall outside the beginning or ending boundaries of stringflavor[: 'fig pieflavor[ : 'in this examplethe first line gets the slice from the beginning of the string up to but not including the fourteenth character the string assigned to flavor has length of sevenso you might expect python to throw an error insteadit ignores any nonexistent indices and returns the entire string "fig piethe third line shows what happens when you try to get slice in which the entire range is out of bounds flavor[ : attempts to get the thirteenth and fourteenth characterswhich don' exist instead of raising an errorpython returns the empty string ("" |
2,305 | note the empty string is called empty because it doesn' contain any characters you can create it by writing two quotation marks with nothing between themempty_string " string with anything in it--even space--is not empty all the following strings are non-emptynon_empty_string non_empty_string non_empty_string even though these strings don' contain any visible charactersthey are non-empty because they do contain spaces you can use negative numbers in slices the rules for slices with negative numbers are exactly the same as the rules for slices with positive numbers it helps to visualize the string as slots with the boundaries labeled with negative numbers- - - - - - - just like beforethe slice [ :yreturns the substring starting at index and going up to but not including for instancethe slice [- :- returns the first three letters of the string "fig pie"flavor[- :- 'fignoticehoweverthat the rightmost boundary of the string does not have negative index the logical choice for that boundary would seem to be the number but that doesn' work |
2,306 | instead of returning the entire string[- : returns the empty stringflavor[- : 'this happens because the second number in slice must correspond to boundary that is to the right of the boundary corresponding to the first numberbut both - and correspond to the leftmost boundary in the figure if you need to include the final character of string in your slicethen you can omit the second numberflavor[- :'fig pieof courseusing flavor[- :to get the entire string is bit odd considering that you can use the variable flavor without the slice to get the same resultslices with negative indices are usefulthoughfor getting the last few characters in string for exampleflavor[- :is "piestrings are immutable to wrap this section uplet' discuss an important property of string objects strings are immutablewhich means that you can' change them once you've created them for instancesee what happens when you try to assign new letter to one particular character of stringword "goalword[ "ftraceback (most recent call last)file ""line in word[ "ftypeerror'strobject does not support item assignment |
2,307 | python throws typeerror and tells you that str objects don' support item assignment if you want to alter stringthen you must create an entirely new string to change the string "goalto the string "foal"you can use string slice to concatenate the letter "fwith everything but the first letter of the word "goal"word "goalword "fword[ :word 'foalfirstyou assign the string "goalto the variable word then you concatenate the slice word[ :]which is the string "oal"with the letter "fto get the string "foalif you're getting different result herethen make sure you're including the colon character (:as part of the string slice review exercises you can nd the solutions to these exercises and many other bonus resources online at realpython com/python-basics/resources create string and print its length using len( create two stringsconcatenate themand print the resulting string create two stringsuse concatenation to add space between themand print the result print the string "zingby using slice notation to specify the correct range of characters in the string "bazinga |
2,308 | manipulate strings with methods manipulate strings with methods strings come bundled with special functions called string methods that you can use to work with and manipulate strings there are numerous string methods availablebut we'll focus on some of the most commonly used ones in this sectionyou'll learn how toconvert string to uppercase or lowercase remove whitespace from string determine if string begins or ends with certain characters let' goconverting string case to convert string to all lowercase lettersyou use the string' lower(method this is done by tacking lower(onto the end of the string itself"jean-luc picardlower('jean-luc picardthe dot tells python that what follows is the name of method-the lower(method in this case note we'll refer to string methods with dot at the beginning of their names for examplelower(is written with leading dot instead of as lower(this makes it easier to differentiate functions that are string methods from built-in functions like print(and type( |
2,309 | string methods don' just work on string literals you can also use lower(on string assigned to variablename "jean-luc picardname lower('jean-luc picardthe opposite of lower(is upper()which converts every character in string to uppercasename upper('jean-luc picardcompare the upper(and lower(string methods to the len(function you saw in the last section aside from the different results of these functionsthe important distinction here is how they're used len(is stand-alone function if you want to determine the length of the name stringthen you call the len(function directlylen(name on the other handupper(and lower(must be used in conjunction with string they do not exist independently removing whitespace from string whitespace is any character that is printed as blank space this includes things like spaces and line feedswhich are special characters that move output to new line sometimes you need to remove whitespace from the beginning or end of string this is especially useful when working with strings that come from user inputwhich may include extra whitespace characters by accident |
2,310 | there are three string methods that you can use to remove whitespace from string rstrip( lstrip( strip(rstrip(removes whitespace from the right side of stringname "jean-luc picard name 'jean-luc picard name rstrip('jean-luc picardin this examplethe string "jean-luc picard has five trailing spaces you use rstrip(to remove trailing spaces from the right-hand side of the string this returns the new string "jean-luc picard"which no longer has the spaces at the end lstrip(works just like rstrip()except that it removes whitespace from the left-hand side of the stringname jean-luc picardname jean-luc picardname lstrip('jean-luc picardto remove whitespace from both the left and the right sides of the string at the same timeuse strip()name jean-luc picard name jean-luc picard name strip('jean-luc picard |
2,311 | it' important to note that none of rstrip()lstrip()or strip(removes whitespace from the middle of the string in each of the previous examplesthe space between "jean-lucand "picardis preserved determine if string starts or ends with particular string when you work with textsometimes you need to determine if given string starts with or ends with certain characters you can use two string methods to solve this problemstartswith(and endswith(let' look at an example consider the string "enterprisehere' how you use startswith(to determine if the string starts with the letters and nstarship "enterprisestarship startswith("en"false you tell startswith(which characters to search for by providing string containing those characters soto determine if "enterprisestarts with the letters and nyou call startswith("en"this returns false why do you think that isif you guessed that startswith("en"returns false because "enterprisestarts with capital ethen you're absolutely rightthe startswith(method is case sensitive to get startswith(to return trueyou need to provide it with the string "en"starship startswith("en"true you can use endswith(to determine if string ends with certain charactersstarship endswith("rise"true |
2,312 | just like startswith()the endswith(method is case sensitivestarship endswith("rise"false note the true and false values are not strings they are special kind of data type called boolean value you'll learn more about boolean values in string methods and immutability recall from the previous section that strings are immutable--they can' be changed once they've been created most string methods that alter stringlike upper(and lower()actually return copies of the original string with the appropriate modifications if you aren' carefulthis can introduce subtle bugs into your program try this out in idle' interactive windowname "picardname upper('picardname 'picardwhen you call name upper()nothing about name actually changes if you need to keep the resultthen you need to assign it to variablename "picardname name upper(name 'picardname upper(returns new string "picard"which is reassigned to the name variable this overrides the original string "picardthat you first assigned to name |
2,313 | use idle to discover additional string methods strings have lots of methods associated with themand the methods introduced in this section barely scratch the surface idle can help you find new string methods to see howfirst assign string literal to variable in the interactive windowstarship "enterprisenexttype starship followed by periodbut do not hit enter you should see the following in the interactive windowstarship now wait for couple of seconds idle displays list of every string methodwhich you can scroll through using the arrow keys related shortcut in idle is the ability to use tab to automatically fill in text without having to type long names for instanceif you type only starship and hit tab then idle automatically fills in starship upper because only one method that begins with belongs to starship this even works with variable names try typing just the first few letters of starship and pressing tab if you haven' defined any other names that share those first lettersthen idle completes the name starship for you review exercises you can nd the solutions to these exercises and many other bonus resources online at realpython com/python-basics/resources write program that converts the following strings to lowercase"animals""badger""honey bee""honey badgerprint each lowercase string on separate line repeat exercise but convert each string to uppercase instead of lowercase |
2,314 | write program that removes whitespace from the following stringsthen print out the strings with the whitespace removedstring filet mignonstring "brisket string cheeseburger write program that prints out the result of startswith("be"on each of the following stringsstring "becomesstring "becomesstring "bearstring beautiful using the same four strings from exercise write program that uses string methods to alter each string so that startswith("be"returns true for all of them interact with user input now that you've seen how to work with string methodslet' make things interactivein this sectionyou'll learn how to get some input from user with input(you'll write program that asks user to input some text and then displays that text back to them in uppercase enter the following into idle' interactive windowinput(when you press enter it looks like nothing happens the cursor moves to new linebut new doesn' appear python is waiting for you to enter something |
2,315 | go ahead and type some text and press enter input(hello there'hello there!the text you entered is repeated on new line with single quotes that' because input(returns as string any text entered by the user to make input( bit more user-friendlyyou can give it prompt to display to the user the prompt is just string that you put between the parentheses of input(it can be anything you wanta worda symbola phrase--anything that is valid python string input(displays the prompt and waits for the user to type something when the user hits enter input(returns their input as string that can be assigned to variable and used to do something in your program to see how input(workstype the following code into idle' editor windowprompt "heywhat' upuser_input input(promptprint("you saiduser_inputpress to run the program the text heywhat' updisplays in the interactive window with blinking cursor the single space at the end of the string "heywhat' upmakes sure that when the user starts to typethe text is separated from the prompt with space when the user types response and presses enter their response is assigned to the user_input variable |
2,316 | here' sample run of the programheywhat' upmind your own business you saidmind your own business once you have input from useryou can do something with it for examplethe following program takes user inputconverts it to uppercase with upper()and prints the resultresponse input("what should shout"shouted_response response upper(print("wellif you insist shouted_responsetry typing this program into idle' editor window and running it what else can you think of to do with the inputreview exercises you can nd the solutions to these exercises and many other bonus resources online at realpython com/python-basics/resources write program that takes input from the user and displays that input back write program that takes input from the user and displays the input in lowercase write program that takes input from the user and displays the number of characters in the input |
2,317 | challengepick apart your user' input write program named first_letter py that prompts the user for input with the string "tell me your password:the program should then determine the first letter of the user' inputconvert that letter to uppercaseand display it back for exampleif the user input is "no"then the program should display the following outputthe first letter you entered wasn for nowit' okay if your program crashes when the user enters nothing as input--that iswhen they just hit enter instead of typing something you'll learn couple of ways to deal with this situation in an upcoming you can nd the solutions to this code challenge and many other bonus resources online at realpython com/python-basics/resources working with strings and numbers when you get user input using input()the result is always string there are many other situations in which input is given to program as string sometimes those strings contain numbers that need to be fed into calculations in this sectionyou'll learn how to deal with strings of numbers you'll see how arithmetic operations work on strings and how they often lead to surprising results you'll also learn how to convert between strings and number types using strings with arithmetic operators you've seen that string objects can hold many types of charactersincluding numbers howeverdon' confuse numerals in string with |
2,318 | actual numbers for instancetry this bit of code out in idle' interactive windownum " num num ' the operator concatenates two strings togetherwhich is why the result of " " is " and not " you can multiply strings by number as long as that number is an integer or whole number type the following into the interactive windownum " num ' num concatenates three instances of the string " and returns the string " compare this operation to arithmetic with numbers when you multiply the number by the number the result is the same as adding three together the same is true for string that is" can be interpreted as " " " in generalmultiplying string by an integer concatenates copies of that string you can move the number on the right-hand side of the expression num to the leftand the result is unchanged num ' what do you think happens if you use the operator between two strings |
2,319 | type " " in the interactive window and press enter " " traceback (most recent call last)file ""line in typeerrorcan' multiply sequence by non-int of type 'strpython raises typeerror and tells you that you can' multiply sequence by non-integer note sequence is any python object that supports accessing elements by index strings are sequences you'll learn about other sequence types in when you use the operator with stringpython always expects an integer on the other side of the operator what do you think happens when you try to add string and number" traceback (most recent call last)file ""line in typeerrorcan only concatenate str (not "int"to str python throws typeerror because it expects the objects on both sides of the operator to be of the same type if an object on either side of is stringthen python tries to perform string concatenation it will only perform addition if both objects are numbers soto add " and get you must first convert the string " to number |
2,320 | converting strings to numbers the typeerror examples in the previous section highlight common problem when applying user input to an operation that requires number and not stringtype mismatches let' look at an example save and run the following programnum input("enter number to be doubled"doubled_num num print(doubled_numif you entered the number at the promptthen you would expect the output to be but in this caseyou would get rememberinput(always returns stringso if you input then num is assigned the string " "not the integer thereforethe expression num returns the string " concatenated with itselfwhich is " to perform arithmetic on numbers contained in stringyou must first convert them from string type to number type there are two functions that you can use to do thisint(and float(int(stands for integer and converts objects into whole numberswhereas float(stands for oating-point number and converts objects into numbers with decimal points here' what using each one looks like in the interactive windowint(" " float(" " notice how float(adds decimal point to the number floatingpoint numbers always have at least one decimal place of precision for this reasonyou can' change string that looks like floating-point number into an integer because you would lose everything after the decimal point |
2,321 | try converting the string " to an integerint(" "traceback (most recent call last)file ""line in valueerrorinvalid literal for int(with base ' even though the extra after the decimal place doesn' add any value to the numberpython won' change into because it would result in loss of precision let' revisit the program from the beginning of this section and see how to fix it here' the code againnum input("enter number to be doubled"doubled_num num print(doubled_numthe issue is on the line doubled_num num because num is string and is an integer you can fix the problem by passing num to either int(or float(since the prompts asks the user to input numberand not specifically an integerlet' convert num to floating-point numbernum input("enter number to be doubled"doubled_num float(num print(doubled_numnow when you run this program and input you get as expected try it outconverting numbers to strings sometimes you need to convert number to string you might do thisfor exampleif you need to build string from some preexisting variables that are assigned to numeric values |
2,322 | as you've already seenconcatenating number with string produces typeerrornum_pancakes " am going to eat num_pancakes pancakes traceback (most recent call last)file ""line in typeerrorcan only concatenate str (not "int"to str since num_pancakes is numberpython can' concatenate it with the string " ' going to eatto build the stringyou need to convert num_pancakes to string using str()num_pancakes " am going to eat str(num_pancakespancakes ' am going to eat pancakes you can also call str(on number literal" am going to eat str( pancakes ' am going to eat pancakes str(can even handle arithmetic expressionstotal_pancakes pancakes_eaten "only str(total_pancakes pancakes_eatenpancakes left 'only pancakes left in the next sectionyou'll learn how to format strings neatly to display values in nicereadable manner before you move onthoughcheck your understanding with the following review exercises |
2,323 | review exercises you can nd the solutions to these exercises and many other bonus resources online at realpython com/python-basics/resources create string containing an integerthen convert that string into an actual integer object using int(test that your new object is number by multiplying it by another number and displaying the result repeat the previous exercisebut use floating-point number and float( create string object and an integer objectthen display them side by side with single print statement using str( write program that uses input(twice to get two numbers from the usermultiplies the numbers togetherand displays the result if the user enters and then your program should print the following textthe product of and is streamline your print statements suppose you have stringname "zaphod"and two integersheads and arms you want to display them in the string "zaphod has heads and armsthis is called string interpolationwhich is just fancy way of saying that you want to insert some variables into specific locations in string one way to do this is with string concatenationname has str(headsheads and str(armsarms'zaphod has heads and armsthis code isn' the prettiestand keeping track of what goes inside or outside the quotes can be tough fortunatelythere' another way of interpolating stringsformatted string literalsmore commonly |
2,324 | known as -strings the easiest way to understand -strings is to see them in action here' what the above string looks like when written as an -stringf"{namehas {headsheads and {armsarms'zaphod has heads and armsthere are two important things to notice about the above example the string literal starts with the letter before the opening quotation mark variable names surrounded by curly braces ({}are replaced by their corresponding values without using str(you can also insert python expressions between the curly braces the expressions are replaced with their result in the stringn "{ntimes {mis { * }' times is it' good idea to keep any expressions used in an -string as simple as possible packing bunch of complicated expressions into string literal can result in code that is difficult to read and difficult to maintain -strings are available only in python version and above in earlier versions of pythonyou can use format(to get the same results returning to the zaphod exampleyou can use format(to format the string like this"{has {heads and {armsformat(nameheadsarms'zaphod has heads and armsf-strings are shorter and sometimes more readable than using format(you'll see -strings used throughout this book |
2,325 | overleaf is web-bases latexsystemmeaning you can write your latexdocuments in your web browseryou co-work and share documents with others for more information about overleafpython books you find other python textbooks within different domains on my python web pagepython bookspython programming this is textbook in python programming with lots of practical examples and exercises you will learn the necessary foundation for basic programming with focus on python python for science and engineering this is textbook in python programming with lots of examplesexercisesand practical applications within mathematicssimulationsetc the focus is on numerical calculations in mathematics and engineering necessary theory is presented in addition to many practical examples python for control engineering this is textbook in python programming with lots of examplesexercisesand practical applications within mathematicssimulationscontrol systemsdaqdatabase systemsetc the focus is on the use of python within measurementsdata collection (daq)control technologyboth analysis of control systems (stability analysisfrequency responseand implementation of control systems (pidetc required theory is presented in addition to many practical examples and exercises in python python for software development this is textbook in python programming with lots of examplesexercisesand practical applications within software systemssoftware developmentsoftware engineeringdatabase systemsweb application desktop applicationsgui applicationsetc the focus is on the use of python for creating modern software systems required theory is presented in addition to many practical examples and exercises in python |
2,326 | the way we create software today has changed dramatically the last yearsfrom the childhood of personal computers in the early to today' powerful devices such as smartphonestablets and pcs the internet has also changed the way we use devices and software we still have traditional desktop applicationsbut web sitesweb applications and socalled apps for smartphonesetc are dominating the software market today we need to find and learn programming languages that are suitable for the new age of programming we have today several thousand different programming languages today guess you will need to learn more than one programming language to survive in today' software market you find lots of programming resources heresoftware engineering software engineering is the discipline for creating software applications systematic approach to the designdevelopmenttestingand maintenance of software the main parts or phases in the software engineering process areplanning requirements analysis design implementation testing deployment and maintenance you find lots of software engineering resources here |
2,327 | getting started with python introduction the new age of programming matlab what is python introduction to python interpreted vs compiled python packages python packages for science and numerical computations anaconda python editors python idle visual studio code spyder visual studio pycharm wing python ide jupyter notebook resources installing python python windows store app installing anaconda installing visual studio code start using python python ide my first python program python shell running python from the console opening the console on macos opening the console on windows add python to path scripting mode run python scripts from the python idle run python scripts from the console (terminalmacos run python scripts from the command prompt in windows |
2,328 | run python scripts from spyder basic python programming basic python program get help variables numbers strings string input built-in functions python standard library using python librariespackages and modules python packages plotting in python subplots exercises ii python programming python programming if else arrays for loops nested for loops while loops exercises creating functions in python introduction functions with multiple return values exercises creating classes in python introduction the init (function exercises creating python modules python modules exercises file handling in python introduction write data to file read data from file logging data to file web resources exercises |
2,329 | introduction to error handling syntax errors exceptions exceptions handling debugging in python installing and using python packages what is pip iii python environments and distributions introduction to python environments and distributions package and environment managers pip conda python virtual environments anaconda anaconda navigator enthought canopy iv python editors python editors spyder visual studio code introduction to visual studio code python in visual studio code visual studio introduction to visual studio work with python in visual studio make visual studio ready for python programming python interactive new python project pycharm wing python ide jupyter notebook jupyterhub microsoft azure notebooks |
2,330 | python for mathematics applications mathematics in python basic math functions exercises statistics introduction to statistics statistics functions in python trigonometric functions polynomials vi resources python resources python distributions python libraries python editors python tutorials python in visual studio vii solutions to exercises |
2,331 | getting started with python |
2,332 | introduction with this textbook you will learn basic python programming the textbook contains lots of examples and self-paced tasks that the users should go through and solve in their own pace you will find additional resources on my blog/web site [ my web site about python issee figure the new age of programming the way we create software today has changed dramatically the last yearsfrom the childhood of personal computers in the early to today' powerful devices such as smartphonestablets and pcs the internet has also changed the way we use devices and software we still have traditional desktop applicationsbut web sitesweb applications and socalled apps for smartphonesetc are dominating the software market today we need to find and learn programming languages that are suitable for the new age of programming we have today several thousand different programming languagesso why should we learn pythoni guess you will need to learn more than one programming language to survive in today' software market python is easy to learnso it it good starting point for new programmers python is an interpretedhigh-levelgeneral-purpose programming language created by guido van rossum and first released in [ |
2,333 | python is fairly old programming language ( compared to many other programming languages like ( )swift ( )java ( )php ( python has during the last years become more and more popular todaypython has become one of the most popular programming languages there are many different rankings regarding which programming language which is most popular in most of these rankingpython is in top one of these rankings is the ieee spectrum' ranking of the top programming languages [ from this ranking we see that python is the most popular programming language in see figure as we see in figure they categorize the different programming languages into the following categoriesweb |
2,334 | mobile enterprise embedded according to figure we see that python can be used to program web applicationsenterprise applications and embedded applications so far python is not used or not optimized for creating mobile applications we have today major mobile platformsios applications are mainly programmed with the swift programming languagewhile android applications are mainly programmed with either java or kotlin another survey is the "stack overflow developer survey [ see figure as we can see from [ and figure python becomes more and more popular year by year based on figure the source [ try to predict the future of pythonsee figure based on the surveys and statistics mention aboveobviously python is programming language that you should learn lets summarizepython is fun to learn and use and it is also named after the british comedy group called monty python python has simple and flexible code structure and the code is easy to read |
2,335 | python is highly extendable due to its high number of free available python packaged and libraries python can be used on all platforms (windowsmacos and linuxpython is multi-purpose and can be used for to program web applicationsenterprise applications and embedded applicationsand within data science and engineering applications the popularity of python is growing fast python is open source and free to use the growing python community makes it easy to find documentationcode examples and get help when needed in generalpython is multipurpose programming language that can be used in many situations but there is not one programming language which is best in all kind of situationsso it is important that you know about and have skills in different languages my list of recommendations (one of many)visual studio and labview graphical programming language well suited for hardware integrationtaking measurements and data logging matlab numerical calculations and scientific computing python numerical calculationsand scientific computingetc web programmingsuch as htmlcssjavascript and server-side framework/programming language like phpasp net ( or vb net)django (python based |
2,336 | databases (such as sql server and mysqland using the structured query language (sqlor the upcoming nosql databases app development for the main platforms ios (xcode using the swift programming languageand android (android studio using the java programming language or kotlin programming languageif you have skills in most of the toolsprogramming languages and frameworks mention aboveyou are well suited for working as full-time programmer or software engineer matlab if you are looking for matlabplease see the following |
2,337 | |
2,338 | what is python introduction to python python is an open source and cross-platform programming languagethat has become increasingly popular over the last ten years it was first released in latest version is cpython is the reference implementation of the python programming language written in ccpython is the default and most widely-used implementation of the language python is multi-purpose programming languages (due to its many extensions)examples are scientific computing and calculationssimulationsweb development (usinge the django web framework)etc python home page [ ]the programming language is maintained and available from (python software foundation)features in one packagewhich includes the python programming language interpreterand basic code editoror an integrated development environmentcalled idle see figure but this is just the python corei the interpreter very basic editorand the minimum needed to create basic python programs typically you will need more features for solving your tasks then you can install and use separate python packages created by third parties these packages need to be downloaded and installed separately (typically you use something called pip)or you choose to usee distribution package like anaconda python is an object-oriented programming language (oop)but you can use python in basic application without the need to know about or use the objectoriented features in python python is an interpreted programming languagethis means that as developer |
2,339 | you write python pyfiles in text editor and then put those files into the python interpreter to be executed depending on the editor you are usingthis is either done automaticallyor you need to do it manually here are some important python sources[ ][ ][ interpreted vs compiled what are the differences between interpreted programming languages and compiled programming languageswhat kind should you chooseand why should you botherprogramming languages generally fall into one of two categoriescompiled or interpreted with compiled languagecode you enter is reduced to set of machine-specific instructions before being saved as an executable file both approaches have their advantages and disadvantages |
2,340 | interpreted programs must be reduced to machine instructions at run-time it is usually easier to develop applications in an interpreted environment because you don' have to recompile your application each time you want to test small section python is an interpreted programming languagewhile / +are translated by running the source code through compileri / +are compiled languages interpreted languagesin contrastmust be parsedinterpretedand executed each time the program is run another example of an interpreted programming language is phpwhich is mainly used to create dynamic web pages and web applications compiled languages are all translated by running the source code through compiler this results in very efficient code that can be executed any number of times the overhead for the translation is incurred just oncewhen the source is compiledthereafterit need only be loaded and executed during the design of an applicationyou might need to decide whether to use compiled language or an interpreted language for the application source code interpreted languagesin contrastmust be parsedinterpretedand executed each time the program is run thusan interpreted language is generally more suited for doing "ad hoccalculations or simulationswhile compiled languages are better for permanent applications where speed is in focus python packages with python you don' get so much out of the box instead of having all of its functionality built into its coreyou need to install different packages for different topics this approach has advantages and disadvantages an disadvantage is that you need to install these packages separately and then later import these modules in your code this is also typical approach for open source softwarebecause everybody can create their own python packages and distribute them in that way you also find python packages for almost everythingfrom scientific computing to web development |
2,341 | to usee distribution package like anacondawhere you typically get the packages you need for scientific computing with anaconda you typically get the same features as with matlab lots of python packages existsdepending on what you are going to solve we have python packages for desktop gui developmentdatabase developmentweb developmentsoftware developmentetc see an overview of applications for pythonsee also the python package index (pypiweb sitehere you can search fordownload and install many hundreds python packages within different topics and applications you can also make your own python packages and distribute them here python packages for science and numerical computations some important python packages for science and numerical computations arenumpy numpy is the fundamental package for scientific computing with python [ scipy scipy is free and open-source python library used for scientific computing and technical computing scipy contains modules for optimizationlinear algebraintegrationinterpolationspecial functionsfftsignal and image processingode solvers and other tasks common in science and engineering [ matplotlib matplotlib is python plotting library [ pandas pandas python data analysis library [ these packages need to be downloaded and installed separatelyor you choose to usee distribution package like anacondawhere you typically get the packages you need for scientific computing with anaconda you typically get the same features as with matlab anaconda anaconda is distribution packagewhere you get python compilerpython packages and the spyder editorall in one package anaconda includes pythonthe jupyter notebookand other commonly used packages for scientific computing and data science |
2,342 | webwikipediaspyder and the python packages (numpyscipymatplotlibmention above ++are included in the anaconda distribution python editors an editor is program where you create your code (and where you can run and test itmost editors have also features for debugging for simple python programs you can use the idle editorbut for more advanced programs better editor is recommended examples of python editorspython idle visual studio code spyder visual studio pycharm wing python ide jupyter notebook these editors are shortly described below and in more detail later in this textbook which editor you should use depends on your backgroundwhat kind of code editors you have used previouslyyour programming skillswhat your are going to develop in pythonetc python idle the programming language is maintained and available from (python software foundation)features in one packagewhich includes the python programming language interpreterand basic code editoror an integrated development environmentcalled idle see figure web |
2,343 | visual studio code visual studio code is source code editor developed by microsoft for windowslinux and macos webresourcesgetting started with python in visual studio code spyder spyder is an open source cross-platform integrated development environment (idefor scientific programming in the python language webwikipediaspyder is included in the anaconda distribution visual studio microsoft visual studio is an integrated development environment (idefrom microsoft it is used to develop computer programsas well as websitesweb appsweb services and mobile apps the deafult (mainprogramming language in visual studio is cbut many other programming languages are supported visual studio is available for windows and macos visual studio (from )has integrated support for pythonit is called "python support in visual studiowebwikipediapycharm pycharm is cross-platformwith windowsmacos and linux versions the community edition is free to usewhile the professional edition (paid versionhas some extra features |
2,344 | wing python ide the wing python ide family of integrated development environments (idesfrom wingware were created specifically for the python programming language different version of wing exists [ ]wing very simplified free versionfor teaching beginning programmers wing personal free version that omits some featuresfor students and hobbyists wing pro full-featured commercial (paidversionfor professional programmers jupyter notebook the jupyter notebook is an open-source web application that allows you to create and share documents that contain live codeequationsvisualizations and text webwikipedia resources here are some useful python resourcesthe official python tutorial the official python documentation python tutorial ( schools com[ installing python the python programming language is maintained and available from (python software foundation) |
2,345 | here you can download the basic python features in one packagewhich includes the python programming language interpreterand basic code editoror an integrated development environmentcalled idle see figure for basic python programming this is good enough for more advanced python programming you typically need better code editor and additional packages for the basic python examples in the beginningthe basic python software fromi suggest you start with the basic python software in order to learn the basicsthen you can upgrade to better editorinstall addition python packages (either manually or or install anaconda where "everythingis includedpython windows store app python is also available in the microsoft store for windows the microsoft store version of python is simplified installer for running scripts and packages microsoft store version of python is very basic but it' good enough to run the simple scripts python microsoft store edition will receive all updates automatically when they are released and no manual action is required from your end in order to install the microsoft store version of python just open microsoft store in windows and search for python installing anaconda the spyder code editor and the python packages (such as numpyscipymatplotlibetcare included in the anaconda distribution download and install frominstalling visual studio code visual studio code code is simple and easy to use editor that can be used for many different programming languages |
2,346 | getting started with python in visual studio code |
2,347 | start using python in this we will start to use python in some simple examples python ide the basic code editoror an integrated development environmentcalled idle see figure other python editors will be discussed more in detail later for now you can use the basic python ide (idleor spyder if you have installed the anaconda distribution package figure python shell python idle editor my first python program we will start using python and create some code examples |
2,348 | lets open your python editor and type the following world listing hello world python example [end of examplean extremely useful command is help()which enters help functionality to explore all the stuff python lets you doright from the interpreter press to close the help window and return to the python prompt you can use python in different wayseither in "interactivemode or in "scriptingmode the python program that you have installed will by default act as something called an interpreter an interpreter takes text commands and runs them as you enter them very handy for trying things out yo can run python interactively in different ways either using the console which is part of the operating system or the python idle and the python shell which is part of the basic python installation from python shell in interactive mode you use the python shell as seen in figure here you type one and one command at time after the "sign in the python shell world running python from the console console (or "terminal"or 'command prompt'is textual way to interact with your os (operating systemthe python program that you have installed will by default act as something called an interpreter an interpreter takes text commands and runs them as you enter them very handy for trying things out below we see how we can run python from the console which is part of the os |
2,349 | opening the console on macos the standard console on macos is program called terminal open terminal by navigating to applicationsthen utilitiesthen double-click the terminal program you can also easily search for it in the system search tool in the top right the command line terminal is tool for interacting with your computer window will open with command line prompt messagesomething like thisl tue dec on computername username just type python at your consolehit enterand you should enter python' interpreter tue dec on hans- -work-macbook- hanshapython python anaconda apr [gcc compatible clang /release on darwin type more information the prompt on the last line indicates that you are now in an interactive python interpeter sessionalso called the "python shellthis is different from the normal terminal command promptyou can now enter some code for python to run tryp world se also figure figure console macos try other python commandse |
2,350 | opening the console on windows window' console is called the command promptnamed cmd an easy way to get to it is by using the key combination windows+ (windows meaning the windows logo button)which should open run dialog then type cmd and hit enter or click ok you can also search for it from the start menu it should look likecu \myusernamejust type python in the command prompthit enterand you should enter python' interpreter see figure figure command prompt windows if you get an error message like this'pythonis not recognized as an internal or external commandoperable program or batch file then you need to add python to your path see instructions below notethis is also an option during the setup while installing you can select "add python exe to paththis option is by default set to "offto get that option you need to select "customize"not using the "defaultinstallation add python to path in the windows menusearch for "advanced system settingsand select view advanced system settings in the window that appearsclick environment variables near the bottom right see figure |
2,351 | in the next windowfind and select the user variable named path and click edit to change its value see figure select "newand add the path where "python exeis located see figure the default location iscu \appdatal programs python python - click save and open the command prompt once more and enter "pythonto verify it works see figure |
2,352 | scripting mode in "scriptingmode you can write python program with multiple python commands and then save it as file pyrun python scripts from the python idle from the python shell you select file new fileor you can open an existing pytho program or python script by selecting file open lets create new script and type in the following print (hello " "worldp "how you in figure we see how this is done as you see we can enter many python commands that together makes python program or python script from the python shell you select run run module or hit in order to run or execute the python script see figure |
2,353 | the idle editor is very basicfor more complicated tasks you typically may prefer to use another editor like spydervisual studio codeetc run python scripts from the console (terminalmacos from the console (terminalon macos cd username downloads python py notemake sure you are at your system command promptwhich will have or at the endnot in python mode (which has instead)see also figure then it responds withhello world how you |
2,354 | run python scripts from the command prompt in windows from command prompt in windowcd cd temp python py notemake sure you are at your system command promptwhich will have at the endnot in python mode (which has instead)see also figure then it responds withhello world how you run python scripts from spyder if you have installed the anaconda distribution package you can use the spyder editor see in the spyder editor we have the script editor to the left and the interactive python shell or the console window to the right see see |
2,355 | figure running python scripts from console window on macos figure running python scripts from console window on macos |
2,356 | |
2,357 | basic python programming basic python program we will start using python and create some code examples we use the basic idle editor (or another python editorexample hello world example lets open your python editor and type the following world listing hello world python example [end of exampleget help an extremely useful command is help()which enters help functionality to explore all the stuff python lets you doright from the interpreter press to close the help window and return to the python prompt variables variables are defined with the assignment operator"=python is dynamically typedmeaning that variables can be assigned without declaring their typeand that their type can change values can come from constantsfrom computation involving values of other variablesor from the output of function python |
2,358 | we use the basic idle (or another python editorand type the followingx listing using variables in python here we define variable and sets the value equal to and then print the result to the screen [end of exampleyou can write one command by time in the idle if you quit idle the variables and data are lost thereforeif you want to write somewhat longer programyou are better off using text editor to prepare the input for the interpreter and running it with that file as input instead this is known as creating script python scripts or programs are save as text file with the extension py example calculations in python we can use variables in calculation like thisx print ( listing using and printing variables in python we can implementing the formula ax like thisa * print (ylisting calculations in python as seen in the examplesyou can use the print(command in order to show the values on the screen [end of example |
2,359 | (sumamountetcyou don need to define the variables before you use them (like you need to to ine / ++/cfigure show these examples using the basic idle editor figure basic python here are some basic rules for python variablesa variable name must start with letter or the underscore character variable name cannot start with number variable name can only contain alpha-numeric characters ( - - and underscores variable names are case-sensitivee amountamount and amount are three different variables numbers there are three numeric types in pythonint float complex |
2,360 | normal coding you don' need to bother example numeric types in python int float complex listing numeric types in python this means you just assign values to variable without worrying about what kind of data type it is type type type listing check data types in python if you use the spyder editoryou can see the data types that variable has using the variable explorer (figure )figure variable editor in spyder [end of examplestrings strings in python are surrounded by either single quotation marksor double quotation marks 'hellois the same as "hellostrings can be output to screen using the print function for exampleprint("hello"example plotting in python below we see examples of using strings in python world print ( print ( print ( print len (aprint lower ( |
2,361 | upper " "jprint ( ("listing strings in python as you see in the examplethere are many built-in functions form manipulating strings in python the example shows only few of them strings in python are arrays of bytesand we can use index to get specific character within the string as shown in the example code [end of examplestring input python allows for command line input that means we are able to ask the user for input example plotting in python the following example asks for the user' namethenby using the input(methodthe program prints the name to the screenp enter your name input ( print hello listing string input [end of example built-in functions python consists of lots of built-in functions some examples are the print( function that we already have used (perhaps without noticing it is actually built-in functionpython also consists of different moduleslibraries or packages these moduleslibraries or packages consists of lots of predefined functions for different topics or areassuch as mathematicsplottinghandling database systemsetc see section for more information and details regarding this in another we will learn to create our own functions from scratch |
2,362 | python standard library python allows you to split your program into modules that can be reused in other python programs it comes with large collection of standard modules that you can use as the basis of your programs the python standard library consists of different modules for handling file /obasic mathematicsetc you don' need to install these separatelybut you need to important them when you want to use some of these modules or some of the functions within these modules the math module has all the basic math functions you needsuch astrigonometric functionssin( )cos( )etc logarithmic functionslog()log ()etc constants like pieinfnanetc etc example using the math module we create some basic examples how to use librarya package or moduleif we need only the sin(function we can do like this from math im por sin ( print (yif we need few functions we can do like this from math im por sin ( print ( cos (xprint (yif we need many functions we can do like this from math im por sin ( print ( cos (xprint (ywe can also use this alternative im po rt math math print ( |
2,363 | im po rt math mt mt print ( [end of examplethere are advantages and disadvantages with the different approaches in your program you may need to use functions from many different modules or packages if you import the whole module instead of just the function(syou need you use more of the computer memory very often we also need to import and use multiple libraries where the different libraries have some functions with the same name but different use other useful modules in the python standard library are statistics (where you have functions like mean()stdev()etc for more information about the functions in the python standard librarysee using python librariespackages and modules rather than having all of its functionality built into its corepython was designed to be highly extensible this approach has advantages and disadvantages an disadvantage is that you need to install these packages separately and then later import these modules in your code some important packages arenumpy numpy is the fundamental package for scientific computing with python scipy scipy is free and open-source python library used for scientific computing and technical computing scipy contains modules for optimizationlinear algebraintegrationinterpolationspecial functionsfftsignal and image processingode solvers and other tasks common in science and engineering matplotlib matplotlib is python plotting library |
2,364 | these packages need to be downloaded and installed separatelyor you choose to usee distribution package like anaconda here you find an overview of the numpy libraryhere you find an overview of the scipy libraryhere you find an overview of the matplotlib libraryyou will learn the basics features in all these libraries we will use all of the in different examples and exercises throughout this textbook example using libraries in this example we use the numpy library im po rt numpy np np print (yin this example we use both the math module in the python standard library and the numpy library im po rt math mt im po rt numpy np mt print ( np print (ynoteas seen in this example we use function called sin(which exists both in the math module in the python standard library and the numpy library in this case they give the same results in this case the following code is not recommended from math im por from numpy imp ort |
2,365 | sin ( print ( sin ( print (yin this case it worksbut assume you have different functions with the same name that have different meaning in different libraries [end of examplepython packages in addition to the python standard librarythere is growing collection of several thousand components (from individual programs and modules to packages and entire application development frameworks)available from the python package index python package index (pypi)here you can download and install individual python packages an easy alternative is the anaconda distributionwhere many of the most used python packages are included anaconda plotting in python typically you need to create some plots or charts in order to make plots or charts in python you will need an external library the most used library is matplotlib matplotlib is python plotting library here you find an overview of the matplotlib libraryif you are familiar with matlab and basic plotting in matlabusing the matplotlib is very similar the main difference from matlab is that you need to import the libraryeither the whole library or one or more functions for simplicity we import the whole library like this im po rt |
2,366 | plot(title(xlabel(ylabel(axis(grid(subplot(legend(show(lets create some basic plotting examples using the matplotlib libraryexample plotting in python in this example we have to arrays with data we want to plot vs we can assume is time series and is the corresponding temperature degrees celsius im po rt [ , plt plot ( yp time temperature degc show we get the following plotwe can also write like this from mp ort [ , plot ( yx time temperature degc show this makes the code simpler to read one problem with this approach appears assuming we import and use multiple libraries and the different libraries have some functions with the same name but different use |
2,367 | [end of examplewe have used basic plotting function in the matplotlib libraryplot(xlabel(ylabel(show(example plotting sine curve im po rt numpy np im po rt [ np plt plot ( yplt xlabel ' plt ylabel ' show this gives the following plot (see figure ) better solution will then be |
2,368 | im po rt im po rt numpy np xstart np increment np xstop np plt plot ( yplt xlabel ' plt ylabel ' show this gives the following plot (see figure )if you want grids you can use the grid(function [end of examplesubplots the subplot command enables you to display multiple plots in the same window typing "subplot( , , )partitions the figure window into an -by- matrix of small subplots and selects the subplot for the current plot the plots are numbered along the first row of the figure windowthen the second rowand so on see figure example creating subplots |
2,369 | we will create and plot sin(and cos(in different subplots im po rt im po rt numpy np xstart np increment np xstop np np plt subplot ( , , plt plot ( ' plt sin plt xlabel ' plt ylabel sin (xplt grid ( show plt subplot ( , , plt plot ( plt cos plt xlabel ' plt ylabel cos (xplt grid ( show [end of example |
2,370 | exercises below you find different self-paced exercises that you should go through and solve on your own the only way to learn python is to do lots of exercisesexercise create sin(xand cos(xin different plots create sin(xand cos(xin different plots you should use all the plotting functions listed below in your codeplot(title(xlabel(ylabel(axis(grid(legend(show([end of exercise |
2,371 | python programming |
2,372 | python programming we have been through the basics in pythonsuch as variablesusing some basic built-in functionsbasic plottingetc you may come far only using these thinsbut to create real applicationsyou need to know about and use features likeif else for loops while loops arrays if you are familiar with one or more other programming languagethese features should be familiar and known to you all programming languages has these features built-inbut the syntax is slightly different from one language to another if else an "if statementis written by using the if keyword here are some examples how you use if sentences in pythonexample using for loops in python if bp than if ap " than = blisting using arrays in python |
2,373 | using if else if bp than belse " than and listing using arrays in python using elif if bp than belif ap " than = blisting using arrays in python notepython uses "elifnot "elseiflike many other programming languages do [end of example arrays an array is special variablewhich can hold more than one value at time here are some examples how you can create and use arrays in pythonexample using for loops in python data data ( data data data data print ( |
2,374 | data append data ( data print (xlisting using arrays in python you define an array like this data you can also use text like this volvo ford you can use arrays in loops like this data print (xyou can return the number of elements in the array like this data you can get specific value inside the array like this index cars index you can use the append(method to add an element to an array data append [end of exampleyou have many built in methods you can use in combination with arrayslike sort()clear()copy()count()insert()remove()etc you should look test all these methods |
2,375 | for loops for loop is used for iterating over sequence guess all your programs will use one or more for loops so if you have not used for loops beforemake sure to learn it now below you see basic example how you can use for loop in python in range ( print the for loop is probably one of the most useful feature in python (or in any kind of programming languagebelow you will see different examples how you can use for loop in python example using for loops in python data data print ( volvo ford for car in print car listing using for loops in python the range(function is handy yo use in for loops (nprint (xthe range(function returns sequence of numbersstarting from by defaultand increments by (by default)and ends at specified number you can also use the range(function like this start #but not in range stop print (xfinallyyou can also use the range(function like this start #but not step top print ( |
2,376 | loop [end of exampleexample using for loops for summation of data you typically want to use for loop for find the sum of given data set data sum #find sum numbers data sum sum sum #find mean average numbers data mean sum/ mean this gives the following results [end of exampleexample implementing fibonacci numbers using for loop in python fibonacci numbers are used in the analysis of financial marketsin strategies such as fibonacci retracementand are used in computer algorithms such as the fibonacci search technique and the fibonacci heap data structure they also appear in biological settingssuch as branching in treesarrangement of leaves on stemthe fruitlets of pineapplethe flowering of artichokean uncurling fern and the arrangement of pine cone in mathematicsfibonacci numbers are the numbers in the following sequence , by definitionthe first two fibonacci numbers are and and each subsequent number is the sum of the previous two some sources omit the initial instead beginning the sequence with two |
2,377 | recurrence relation fn fn- fn- ( with seed valuesf we will write python script that calculates the first fibonacci numbers the python script becomes like this fib fib print fib print fib ( - + fib fib fib fib next print fib next listing fibonacci numbers using for loop in python alternative solution fib [ ( - + + append print fib listing fibonacci numbers using for loop in python alt another alternative solution fib (nf append fib [ fib [ |
2,378 | ( - + + + print fib listing fibonacci numbers using for loop in python alt another alternative solution im po rt numpy np np ( fib [ fib [ ( - + + + print fib listing fibonacci numbers using for loop in python alt [end of examplenested for loops in python and other programming languages you can use one loop inside another loop syntax for nested for loops in python in sequence in sequence statements statements simple example in range ( in range ( print kexercise prime numbers the first prime numbers (all the prime numbers less than are |
2,379 | other divisorit cannot be prime natural number ( etc is called prime number (or primeif it is greater than and cannot be written as product of two natural numbers that are both smaller than it create python script where you find all prime numbers between and tipi guess this can be done in many different waysbut one way is to use nested for loops [end of exercise while loops the while loop repeats group of statements an indefinite number of times under control of logical condition example using while loops in python while (mm listing using while loops in python [end of example exercises below you find different self-paced exercises that you should go through and solve on your own the only way to learn python is to do lots of exercisesexercise plot of dynamic system given the autonomous systemx ax wherea= ( |
2,380 | the solution for the differential equation isx(teat ( set = and the initial condition ( )= create script in python py filewhere you plot the solution (tin the time interval < < add gridand proper title and axis labels to the plot [end of exercise |
2,381 | creating functions in python introduction function is block of code which only runs when it is called you can pass dataknown as parametersinto function function can return data as result previously we have been using many of the built-in functions in python if you are familiar with one or more other programming languagecreating and using functions should be familiar and known to you all programming languages has the possibility to create functionsbut the syntax is slightly different from one language to another some programming languages uses the term method instead of function functions and methods behave in the same mannerbut you could say that methods are functions that belongs to class we will learn more about classes in scripts vs functions it is important to know the difference between script and function scriptsa collection of commands that you would execute in the editor used for automating repetitive tasks functionsoperate on information (inputsfed into them and return outputs have separate workspace and internal variables that is only valid inside the function |
2,382 | python have lots of built-in functionsbut very often we need to create our own functions (we could refer to these functions as user-defined functionsin python function is defined using the def keyword functionname return example create function in separate file below you see simple function created in python add return listing basic python function the function adds numbers the name of the function is addand it returns the answer using the return statement the statement return [expressionexits functionoptionally passing back an expression to the caller return statement with no arguments is the same as return none note that you need to use colon ":at the end of line where you define the function note also the indention used add here you see python script where we use the function add return add print listing creating and using python function |
2,383 | example create function in separate file we start by creating separate python file (myfunctions pyfor the function def average ( / listing function calculating the average nextwe create new python file ( testaverage pywhere we use the function we created from im po rt average ( print listing test of average function [end of example functions with multiple return values typically we want to return more than one value from function example create function function with multiple return values create the following example def stat ( totalsum #find sum numbers data totalsum totalsum #find mean average numbers data mean / mean |
2,384 | data mean data mean listing function with multiple return values [end of example exercises below you find different self-paced exercises that you should go through and solve on your own the only way to learn python is to do lots of exercisesexercise create python function create function calcaverage that finds the average of two numbers [end of exerciseexercise create python functions for converting between radians and degrees since most of the trigonometric functions require that the angle is expressed in radianswe will create our own functions in order to convert between radians and degrees it is quite easy to convert from radians to degrees or from degrees to radians we have that [radians [degrees( this givesd[degreesr[radiansx ( and ( create two functions that convert from radians to degrees ( ( )and from degrees to radians ( ( )respectively [radiansd[degreesx these functions should be saved in one python file py test the functions to make sure that they work as expected |
2,385 | exercise create function that implementing fibonacci numbers fibonacci numbers are used in the analysis of financial marketsin strategies such as fibonacci retracementand are used in computer algorithms such as the fibonacci search technique and the fibonacci heap data structure they also appear in biological settingssuch as branching in treesarrangement of leaves on stemthe fruitlets of pineapplethe flowering of artichokean uncurling fern and the arrangement of pine cone in mathematicsfibonacci numbers are the numbers in the following sequence , by definitionthe first two fibonacci numbers are and and each subsequent number is the sum of the previous two some sources omit the initial instead beginning the sequence with two in mathematical termsthe sequence fn of fibonacci numbers is defined by the recurrence relation fn fn- fn- ( with seed valuesf create function that implementing the first fibonacci numbers [end of exerciseexercise prime numbers the first prime numbers (all the prime numbers less than are by definition prime number has both and itself as divisor if it has any other divisorit cannot be prime natural number ( etc is called prime number (or primeif it is greater than and cannot be written as product of two natural numbers that are both smaller than it tipi guess this can be implemented in many different waysbut one way is to use nested for loops |
2,386 | or not you can check the function in the command window like this number number then python respond with true or false [end of exercise |
2,387 | creating classes in python introduction python is an object oriented programming (ooplanguage almost everything in python is an objectwith its properties and methods the foundation for all object oriented programming (ooplanguages are classes to create classuse the keyword class classname example simple class example we will create simple class in python car model volvo blue car model print car color listing simple python class the results will be in this case volvo blue |
2,388 | more examples [end of exampleexample python class lets create the following python code car model " car model volvo blue model model ford green model listing python class example you should try these examples [end of example the init (function in python all classes have built-in function called init ()which is always executed when the class is being initiated in many other oop languages we call this the constructor exercise the init (function we will create simple example where we use the init (function to illustrate the principle we change our previous car example like this car def init model model model color color car ford green model print car |
2,389 | car volvo blue model print car listing python class constructor example lets extend the class by defining function as welld car car def init model model model color color def displaycar model print color lets using the class car "red car displaycar ( car ford green model print car car volvo blue model print car =black car displaycar (listing python class with function as you see from the code we have now defined class "carthat has class variables called "modeland "color"and in addition we have defined function (or methodcalled "displaycar()its normal to use the term "methodfor functions that are defined within class you declare class methods like normal functions with the exception that the first argument to each method is self to create instances of classyou call the class using class name and pass in whatever arguments its init (method accepts for example |
2,390 | car "red[end of exampleexercise create the class in separate python file we start by creating the class and then we save the code in "car py" car car def init model model model color color def displaycar model print color listing define python class in separate file then we create python script (testcar pywhere we are using the classi car from car im por car lets using the class car "red car displaycar ( car ford green model print car car volvo blue model print car =black car displaycar (listing script that is using the class notice the following line at the top from car im por car [language=python[end of example |
2,391 | exercises below you find different self-paced exercises that you should go through and solve on your own the only way to learn python is to do lots of exercisesexercise create python class create python class where you calculate the degrees in fahrenheit based on the temperature in celsius and vice versa the formula for converting from celsius to fahrenheit istf (tc / ( the formula for converting from fahrenheit to celsius istc (tf ( / ( [end of exercise |
2,392 | creating python modules as your program gets longeryou may want to split it into several files for easier maintenance you may also want to use handy function that you have written in several programs without copying its definition into each program to support thispython has way to put definitions in file and use them in script or in an interactive instance of the interpreter (the python console window python modules module is file containing python definitions and statements the file name is the module name with the suffix py appended python allows you to split your program into modules that can be reused in other python programs it comes with large collection of standard modules that you can use as the basis of your programs as we have seen examples of in previous not it is time to make your own modules from scratch consider module to be the same as code library file containing set of functions you want to include in your application previously you have been using different moduleslibraries or packages created by the python organization or by others here you will create your own modules from scratch example create your first python module we will create python module with functions the first function should convert from celsius to fahrenheit and the other function should convert from fahrenheit to celsius the formula for converting from celsius to fahrenheit istf (tc / ( |
2,393 | tc (tf ( / ( firstwe create python module with the following functions (fahrenheit py) tc tf tc tf tf tc tf tc listing fahrenheit functions thenwe create python script for testing the functions (testfahrenheit py) from mp ort tc tf tc tf tf tc tf tc listing python script testing the functions the results becomes fahrenheit celsius exercises below you find different self-paced exercises that you should go through and solve on your own the only way to learn python is to do lots of exercisesexercise create python module for converting between radians and degrees since most of the trigonometric functions require that the angle is expressed in radianswe will create our own functions in order to convert between radians |
2,394 | it is quite easy to convert from radians to degrees or from degrees to radians we have that [radians [degrees( this givesd[degreesr[radiansx ( [radiansd[degreesx ( and create two functions that convert from radians to degrees ( ( )and from degrees to radians ( ( )respectively these functions should be saved in one python file py test the functions to make sure that they work as expected you can choose to make new py file to test these functions or you can use the console window [end of exercise |
2,395 | file handling in python introduction python has several functions for creatingreadingupdatingand deleting files the key function for working with files in python is the open(function the open(function takes two parametersfilenameand mode there are four different methods (modesfor opening file"xcreate creates the specified filereturns an error if the file exists "wwrite opens file for writingcreates the file if it does not exist "rread default value opens file for readingerror if the file does not exist "aappend opens file for appendingcreates the file if it does not exist in addition you can specify if the file should be handled as binary or text mode "ttext default value text mode "bbinary binary mode ( images write data to file to create new file in pythonuse the open(methodwith one of the following parameters"xcreate creates the specified filereturns an error if the file exists "wwrite opens file for writingcreates the file if it does not exist "aappend opens file for appendingcreates the file if it does not exist |
2,396 | "wwrite opens file for writingcreates the file if it does not exist "aappend opens file for appendingcreates the file if it does not exist example write data to file open " data helo world data close (listing write data to file [end of example read data from file to read to an existing fileyou must add the following parameter to the open(function"rread default value opens file for readingerror if the file does not exist example read data from file open data data close (listing read data from file [end of example logging data to file typically you want to write multiple data to thee assume you read some temperature data at regular intervals and then you want to save the temperature values to file example logging data to file |
2,397 | data open " data record value write record \ close (listing logging data to file [end of exampleexample read logged data from file open for record in \nprint record close (listing read logged data from file [end of example web resources below you find different useful resources for file handling python file handling schoolreading and writing files python org exercises below you find different self-paced exercises that you should go through and solve on your own the only way to learn python is to do lots of exercisesexercise data logging assume you have the following data you want to log to file as shown in table log these data to file create another python script that reads the same data |
2,398 | exercise data logging assume you read data from temperature sensor every seconds for period of let say minutes log the data to file you can use the random generator in python an example of how to use the random generator is shown below im po rt random in range ( data random data listing read data from file make sure to log both the time and the temperature value create another python script that reads the same data you should also plot the data you read from the file [end of exercise |
2,399 | time value |
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