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(python2.1-tut.info)if Statements

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`if' Statements
===============

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

     >>> x = int(raw_input("Please enter a number: "))
     >>> 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.