1 

     2 ===============

     3  Python syntax

     4 ===============

     5 .. contents::

     6    :local:

     7 

     8 List comprehension

     9 ==================

    10 

    11 List comprehension produce complete list with compact syntax::

    12 

    13   [x**2 for x in xrange(1,10)]

    14   [x+y for x in xrange(1,10) for y in xrange(1,10)]

    15   [x-y for x in xrange(1,10) for y in xrange(1,10) if x>y]

    16 

    17   xlist = [x**2 for x in xrange(1,10)]

    18   print xlist[0], xlist[2], xlist[-1]

    19   print xlist[2:4]

    20   print sum(xlist), sum(xlist)

    21 

    22 Generator expression

    23 ====================

    24 

    25 Generator expression produce generator with compact syntax::

    26 

    27   (x**2 for x in xrange(1,10))

    28   (x+y for x in xrange(1,10) for y in xrange(1,10))

    29 

    30   print [x for x in (x**2 for x in xrange(1,10))]

    31 

    32   xgen = (x**2 for x in xrange(1,10))

    33   try:

    34       xgen[0]

    35   except TypeError:

    36       print "'generator' object has no attribute '__getitem__'"

    37   print sum(xlist), sum(xlist)

    38 

    39 Parentheses is required only if expression is ambiguous.

    40