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4.1 if Statements

Perhaps the most well-known statement type is the if statement. For example:

    >>> x = int(raw_input("Please enter an integer: "))
    >>> if x < 0:
    ...      x = 0
    ...      print 'Negative changed to zero'
    ... elif x == 0:
    ...      print 'Zero'
    ... elif x == 1:
    ...      print 'Single'
    ... else:
    ...      print 'More'
    ... 

There can be zero or more elif parts, and the else part is optional. The keyword `elif' is short for `else if', and is useful to avoid excessive indentation. An if ... elif ... elif ... sequence is a substitute for the switch or case statements found in other languages.