(tuples or listssay)they can be conveniently unpacked into variables in the for loop statementfor abc in iteratordo something while loops while loop specifies condition and block of code that is to be executed until the condition evaluates to false or the loop is explicitly ended with breakx total while if total break total + / pass pass is the "no-opstatement in python it can be used in blocks where no action is to be takenit is only required because python uses whitespace to delimit blocksif print 'negative!elif = todoput something smart here pass elseprint 'positive!it' common to use pass as place-holder in code while working on new piece of functionalitydef (xyz)todoimplement this functionpass exception handling handling python errors or exceptions gracefully is an important part of building robust programs in data analysis applicationsmany functions only work on certain kinds of input as an examplepython' float function is capable of casting string to floating point numberbut fails with valueerror on improper inputsin [ ]float(' 'out[ ] in [ ]float('something'valueerror traceback (most recent call lastin ( appendixpython language essentials www it-ebooks info