By Austin Laudenslager AN INTRODUCTION TO PYTHON

 Created in 1989 by Guido van Rossum  Highly extensible  Aims to create beautiful, readable code  Variables are assigned a type automatically  Blocks of code are defined by whitespace  Arguments from the console are stored in the argv variable, which can be accessed using sys.argv[n]  _ variable can be used in interactive mode to refer to the previous expression – it can not be assigned a value manually PYTHON

 +, -, *, % work the same as C++/Java  / returns a float, // performs integer division  ** can be used to calculate powers  Use parenthesis for grouping () MATH TIP: Integers and floating point numbers may both be used in the same equation without typecasting, computes to floating point number. >>>5+5>>>5*5>>>7% >>>5/2>>>5// >>>5**2>>>10** >>>5*2+2>>>5*(2+2) 1220

 Can be enclosed in either single or double quotes  \ can be used to escape quotes, \n is new line  Use print() to display strings, r ignores special characters  Triple quotes allows strings to span multiple lines STRINGS >>> ‘string’ >>> “string” >>>’I can\’t’>>>’Line one\nLine two’ ‘I can’t”Line one Line two >>>Print(‘some\name’)>>>print(r’some\name’) somesome\name ame >>>print(“”” Line one Line two “””) Line one Line two

 + allows for concatenation, * performs repetition  Strings are indexed from the left AND right  Use [n:m] to slice strings  Use len() to return the length of a string STRING OPERATIONS >>> ‘string’ + ‘one’>>> ‘string’ * 3 ‘stringone’‘stringstringstring’ >>>word=‘Python’>>>word[0]>>>word[-2] ‘P’‘0’ >>>word[2:4]>>>word[:2] ‘th’‘Py’ >>>len(word) 6 TIP: Strings are immutable: Word[3] = ‘z’ will NOT work.

 Declared as a list of comma seperated values  Can be indexed, sliced, and concatenated the same as strings  ARE mutable, can be changed by index OR slice  Can use function append() to add items to the end of a list  Funtion len() returns length of list  Can nest lists: LISTS >>>numbers = [1, 2, 3]>>>strings = [‘a’, ‘b’, ‘c’] >>>number.append(1)>>>len(number) [4, 8, 7, 3, 1]5 >>>nest = [numbers, words] >>>nest[0]>>>nest[0][3] [4, 8, 7, 3, 1]3 >>>numbers[1] = 5>>>numbers[0:2] = [4, 8, 7] [1, 5, 3][4, 8, 7, 3]

 While, if, elif, else work like in C++  Unlike C++, for loops iterate over items of a sequence numbers = [6, 2, 4]  Use range(n) to iterate over a sequence of number  Break statement ends current loop  Else can also be used with loops  Continue statement skips to the next iteration of the loop  Pass can be used to represent a statement where no action is needed CONTROL FLOW STATEMENTS >>>for n in numbers: TIP: Control flow statements do NOT use parenthesis in Python. >>>for i in range(10) IMPORTANT: Python uses whitespace indentation, levels of code are determined by indentation, not grouped by curly braces!

 All functions are of the def, or definition type  Can return any type of object  Returns none by default  Example function:  n can be of any type and will be returned as the same type  Can also include optional arguments with default values:  Can be called with multiply(n) or multiply(n,m) FUNCTIONS >>> def returnVal(n): print(n) return n >>> def multiply(n, count=2): return n*count

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