Pyhon中的range()函数用法

range function generates lists containing arithmetic progressions:
>>> range(10)
     [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
It is possible to let the range start at another number, or to specify a different increment (even negative; sometimes this is called the `step'):

>>> range(5, 10)
     [5, 6, 7, 8, 9]
>>> range(0, 10, 3)
     [0, 3, 6, 9]
>>> range(-10, -100, -30)
     [-10, -40, -70]

To iterate over the indices of a sequence, combine range() and len() as follows:

>>> a = ['Mary', 'had', 'a', 'little', 'lamb']
>>> for i in range(len(a)):
...     print i, a[i]
...
    0 Mary
    1 had
    2 a
    3 little
    4 lamb