Control Statements:if statements: An if statement allows code to be executed or not based on the result of a comparison. If thecondition evaluates to True, then the statements of the indented body is executed. If the condition is False,then the body is skipped. The syntax of if statements is:if <condition>: statementT1 statementT2elif <condition2>: statement statementelse: statementF1 statementF2if <condition>: statementT1 statementT2else: statementF1 statementF2if <condition>: statement1 statement2 statement3 Typically, the condition involves comparing “stuff” using relational operators ( <, >, ==, <=, >=, != ). Complex conditions might involve several comparisons combined using Boolean operators: not, or, and.For example, we might want to print “Your grade is B.” if the variable score is less than 90, but greater than orequal to 80. if score < 90 and score >= 80: print “Your grade is B.”The precedence for mathematical operators, Boolean operators, and comparisons are given in the table.. for loop: the for loop iterates once for each item in some sequence type (i.e, list, tuple, string). for character in 'house': print characterfor value in [1, 3, 9, 7]: print valueOften the for loop iterates over a list generated by the built-in range function which has the syntax of:range([start,] end, [, step]), where [ ] are used to denote optional parameters. Some examples: range(5) generates the list [0, 1, 2, 3, 4] range(2,7) generates the list [2, 3, 4, 5, 6] range(10,2,-1) generates the list [10, 9, 8, 7, 6, 5, 4, 3]Since the list generated by the range function needs to be stored in memory, a more efficient xrangefunction is typically using in for loops to generate each value one at a time for each iteration of the loop. Forexample:for count in xrange(1,6): print count, " " ,print "\nDone"Name:_________________________Python Summary Page 1 = (assignment)orandnot<, >, ==, <=, >=, !=, <>, is, is not +, - (add, sub)*, /, % (remainder) +, - (unary pos. & neg.) ** (exponential)Operator(s)highestlowest1 2 3 4 5Donewhile loop: A while statement allows code to be executed repeated (zero or more times) as long as thecondition evaluates to True. The syntax of a while statement is:while <condition>: statement1 statement2 statement3An infinite loop is one that would loop forever. (FYI, in a Python shell ctrl-c (^c)can be used to kill the running program.) Most infinite loops are caused by programmer error, but sometimesthey are intentional. The following “sentinel-controlled” code uses an infinite loop and a break statement thatimmediately causes control to exit the loop.total = 0counter = 0while True: # an infinite loop score = input("Enter a score (or negative value to exit): ") if score < 0: break total += score counter += 1print "Average is", float(total)/counterStrings: Strings in Python are sequential collections of only characters. Strings are immutable (i.e., cannot bechanged), so new strings are generated by string operations. Operations on strings (or any sequence collection)include:8len( myString )How many items are in thestring?len(string)LengthTrue‘ell’ in myStringAsk whether a substring is ina stringinMembership‘catcatcat’aString * 3Concatenate a repeatednumber of times*Repetition‘Hello!!!cat’myString + aStringCombine strings together+Concatenation‘ello’myString[ 1:5 ]Extract a part of the string[ : ]Slicing‘e’myString[1]Access the element specifiedby the index[ <index> ]IndexingResult ofExampleExamplemyString = “Hello!!!”aString = “cat”ExplanationOperatorOperationIndexing of strings starts with 0 on the left end, and -1 on the right end: 1111 01234567890123cheer = ‘GO Panthers!!!’ -4-3-2-1Omitted indexes in a slice means “from the end.” For example, cheer[:4] generates ‘GO P’.Omitted indexes in a slice means “from the end.” For example, cheer[-4:] generates ‘s!!!’.Name:_________________________Python Summary Page 2Is condition true? Statements in loop bodyFalseTrueString objects also have the following methods: (the string module can be imported to provide moreoperations.)Returns a string with all occurrences of substring old replaced bysubstring new. An additional integer parameter can specify thenumber of replacements to perform, e.g.,myString.replace(old,new,3)myString.replace(old,new)replaceReturns the starting index of the first occurrence of sub.(Optional parameters: myString.find(sub [, start [, end] ] )myString.find(sub)findReturns a list of substrings of myString splits at whitespacecharacters.An optional string parameter can supply characters to split on.myString.split( )splitReturns True if myString contains only letters; otherwise it returnsFalsemyString.isalpha( )isalphaReturns True if myString contains only digits; otherwise it returnsFalsemyString.isdigit( )isdigitReturns True if myString starts with the substring sub; otherwise itreturns False myString.startswith(sub)startswithReturns True if myString ends with the substring sub; otherwise itreturns False myString.endswith(sub)endswithReturns number of occurrences of sub in myString(Optional parameters: myString.count(sub [, start [, end] ] ) myString.count(sub)countReturns a string with leading and trailing whitespace (space, tab,new-line) chars. removed. An optional string parameter can beused to supply characters to strip instead of whitespace.myString.strip( )stripReturns a string with myString in all lower-case charactersmyString.lower( )lowerReturns a string with myString in all upper-case charactersmyString.upper( )upperReturns a string with myString right-justified in a field of size wmyString.rjust(w)rjustReturns a string with myString left-justified in a field of size wmyString.ljust(w)ljustReturns a string with myString centered in a field of size wmyString.center(w)centerExplanationUsageMethodLists: A Python list is also a sequence collection, but a list can contain items of any type (e.g., character,strings, integers, floats, other lists, etc. ), and lists are mutable. Lists are represented by comma-separated valuesenclosed in square brackets (‘[’, ‘]’). Operations on lists (or any sequence collection, e.g., strings) include:4len( myList )How many items are inthe list?len(list)LengthFalse3 in myListAsk whether an item isin a listinMembership[8,