introduction to python program for which the maximum running time is bounded by the length of the program is said to run in constant time this does not mean that each time it is run it executes the same number of steps it means that there exists constantksuch that the program is guaranteed to take no more than steps to run this implies that the running time does not grow with the size of the input to the program constant-time programs are quite limited in what they can do considerfor examplewriting program to tally the votes in an election it would be truly surprising if one could write program that could do this in time that was independent of the number of votes cast in factone can prove that it is impossible to do so the study of the intrinsic difficulty of problems is the topic of computational complexity we will return to this topic several times in this book fortunatelywe need only one more programming language constructiterationto be able to write programs of arbitrary complexity we get to that in section finger exercisewrite program that examines three variables--xyand -and prints the largest odd number among them if none of them are oddit should print message to that effect strings and input objects of type str are used to represent strings of characters literals of type str can be written using either single or double quotese 'abcor "abcthe literal ' denotes string of charactersnot the number one hundred twenty-three try typing the following expressions in to the python interpreter (remember that the is promptnot something that you type)' * *' + ' '+'athe operator is said to be overloadedit has different meanings depending upon the types of the objects to which it is applied for exampleit means addition when applied to two numbers and concatenation when applied to two strings the operator is also overloaded it means what you expect it to mean when its operands are both numbers when applied to an int and strit duplicates the str for examplethe expression *'johnhas the value unlike many programming languagespython has no type corresponding to character insteadit uses strings of length