false none true and as assert break class continue def del elif else except finally for from global if import in is lambda nonlocal not or pass raise return try while with yield table python keywords expressions programs manipulate data so farwe have seen two different kinds of data in our example programsnumbers and text we'll examine these different data types in great detail in later for nowyou just need to keep in mind that all data has to be stored on the computer in some digital formatand different types of data are stored in different ways the fragments of program code that produce or calculate new data values are called expressions the simplest kind of expression is literal literal is used to indicate specific value in chaos py you can find the numbers and the convert py program contains and these are all examples of numeric literalsand their meaning is obvious representswell (the number our programs also manipulated textual data in some simple ways computer scientists refer to textual data as strings you can think of string as just sequence of printable characters string literal is indicated in python by enclosing the characters in quotation marks (""if you go back and look at our example programsyou will find number of string literals such as"helloand "enter number between and these literals produce strings containing the quoted characters note that the quotes themselves are not part of the string they are just the mechanism to tell python to create string the process of turning an expression into an underlying data type is called evaluation when you type an expression into python shellthe shell evaluates the expression and prints out textual representation of the result consider this small interaction "hello'hello" ' notice that when the shell shows the value of stringit puts the sequence of characters in single quotes this is way of letting us know that the value is actually textnot number (or other data typein the last interactionwe see that the expression " produces stringnot number in this casepython is actually storing the characters " and " ,not representation of the number