Python 3 Beginner's Reference Cheat Sheet                                                                                                                        Alvaro Sebastian 
                                                                                                                                                                                        http://www.sixthresearcher.com 
                             Main data types                                                            List operations                                                             List methods 
           boolean = True / False                                                     list = []        defines an empty list                                list.append(x)          adds x to the end of the list 
           integer = 10                                                               list[i] = x      stores x with index i                                list.extend(L)          appends L to the end of the list 
           float = 10.01                                                              list[i]          retrieves the item with index I                      list.insert(i,x)        inserts x at i position 
           string = “123abc”                                                          list[-1]         retrieves last item 
           list = [ value1, value2, … ]                                                                                                                     list.remove(x)          removes the first list item whose 
           dictionary = { key1:value1, key2:value2, …}                                list[i:j]        retrieves items in the range i to j                                          value is x 
                                                                                      del list[i]      removes the item with index i                        list.pop(i)             removes the item at position i and 
                 Numeric                           Comparison                                                                                                                       returns its value 
                operators                            operators                                    Dictionary operations                                     list.clear()            removes all items from the list 
                                                                                                                                                            list.index(x)           returns a list of values delimited 
           +       addition                   ==       equal                          dict = {}          defines  an empty dictionary                                               by x 
           -       subtraction                !=       different                      dict[k] = x        stores x associated to key k                       list.count(x)           returns a string with list values  
           *       multiplication             >        higher                         dict[k]            retrieves the item with key k                                              joined by S 
           /       division                                                                                                                                 list.sort()             sorts list items 
           **      exponent                   <        lower                          del dict[k]        removes the item with key k                        list.reverse()          reverses list  elements 
           %       modulus                    >=       higher or equal                                                                                      list.copy()             returns a copy of the list 
           //      floor division             <=       lower or equal                                  String methods 
                 Boolean                               Special                        string.upper()               converts to uppercase                                      Dictionary methods 
                operators                           characters                        string.lower()               converts to lowercase 
           and       logical AND              #               coment                  string.count(x)              counts how many                          dict.keys()              returns a list of keys 
                                                                                                                   times x appears                          dict.values()            returns a list of values 
           or        logical OR               \n              new line                string.find(x)               position of the x first                  dict.items()             returns a list of pairs (key,value) 
           not       logical NOT              \         scape char                                           occurrence                               dict.get(k)              returns the value associtated to 
                                                                                      string.replace(x,y)          replaces x for y                                                  the key k 
                             String operations                                        string.strip(x)              returns a list of values                 dict.pop()               removes the item associated to 
                                                                                                                   delimited by x                                                    the key and returns its value 
           string[i]        retrieves character at position i                         string.join(L)               returns a string with L                  dict.update(D)           adds keys-values (D) to dictionary 
                                                                                                                   values joined by string                  dict.clear()             removes all keys-values from the 
           string[-1]       retrieves last character                                  string.format(x)             returns a string that                                             dictionary 
           string[i:j]      retrieves characters in range i to j                                                   includes formatted x                     dict.copy()              returns a copy of the dictionary 
           Legend: x,y stand for any kind of data values, s for a string, n for a number, L for a list where  i,j are list indexes, D stands for a dictionary and k is a dictionary key. 
                          Python 3 Beginner's Reference Cheat Sheet                                                                                            Alvaro Sebastian 
                                                                                                                                                        http://www.sixthresearcher.com 
                                Built-in functions                                        Conditional                              Loops                              Functions 
                                                                                          statements 
             print(x, sep='y')      prints x objects separated by y                  if  :                     while :                  def function(): 
             input(s)               prints s and waits for an input                                                                                        
                                    that will be returned                            else if  :                                                             return  
                                                                                                                    for  in : 
             len(x)                 returns the length of x (s, L or D)              …                                             
                                                                                     else:                                                                            Modules 
             min(L)                 returns the minimum value in L                                                  for  in 
             max(L)                 returns the maximum value in L                                                        range(start,stop,step):              import module 
             sum(L)                 returns the sum of the values in L               if  in :                                               module.function() 
             range(n1,n2,n)         returns a sequence of numbers                                                         for key, value in                    from module import * 
                                    from n1 to n2 in steps of n                        Data validation                    dict.items():                        function() 
                                                                                                                                 
             abs(n)                 returns the absolute value of n                    try:                                                                         Reading and  
             round(n1,n)            returns the n1 number rounded                                                       Loop control                          writing files 
                                    to n digits                                        except :                         statements 
                                                                                                                                                          f = open(,‘r') 
             type(x)                returns the type of x (string, float,              else:                           break          finishes loop             f.read() 
                                    list, dict …)                                                                               execution                 f.readline() 
             str(x)                 converts x to string                                                               continue       jumps to next             f.close() 
                                                                                     Working with files                               iteration 
             list(x)                converts x to a list                                 and folders                   pass           does nothing             f = open(,’r’) 
             int(x)                 converts x to a integer number                                                                                             for line in f: 
                                                                                     import os                              Running external                           
             float(x)               converts x to a float number                     os.getcwd()                                programs                       f.close() 
             help(s)                prints help about x                              os.makedirs()                 import os                             f = open(,'w') 
                                                                                     os.chdir()                                                          f.write() 
             map(function, L)       Applies function to values in L                  os.listdir()                  os.system()                  f.close() 
          Legend: x,y stand for any kind of data values, s for a string, n for a number, L for a list where  i,j are list indexes, D stands for a dictionary and k is a dictionary key.