python内置函数4-enumerate()
Help on> class enumerate(object)|enumerate(iterable[, start]) -> iterator for index, value of iterable
|
|Return an enumerate object.iterable must be another object that supports
|iteration.The enumerate object yields pairs containing a count (from
|start, which defaults to zero) and a value yielded by the iterable argument.
|enumerate is useful for obtaining an indexed list:
| (0, seq), (1, seq), (2, seq), ...
|
|Methods defined here:
|
|__getattribute__(...)
| x.__getattribute__('name') <==> x.name
|
|__iter__(...)
| x.__iter__() <==> iter(x)
|
|next(...)
| x.next() -> the next value, or raise StopIteration
|
|----------------------------------------------------------------------
|Data and other attributes defined here:
|
|__new__ = <built-in method __new__ of type object>
| T.__new__(S, ...) -> a new object with type S, a subtype of T
enumerate(sequence, start=0)
Return an enumerate object. sequence must be a sequence, an iterator, or some other object which supports iteration. The next() method of the iterator returned by enumerate() returns a tuple containing a count (from start which defaults to 0) and the values obtained from iterating over sequence:
>>>
>>> seasons = ['Spring', 'Summer', 'Fall', 'Winter']
>>> list(enumerate(seasons))
[(0, 'Spring'), (1, 'Summer'), (2, 'Fall'), (3, 'Winter')]
>>> list(enumerate(seasons, start=1))
[(1, 'Spring'), (2, 'Summer'), (3, 'Fall'), (4, 'Winter')]
Equivalent to:
def enumerate(sequence, start=0):
n = start
for elem in sequence:
yield n, elem
n += 1
中文说明：
用于遍历序列中的元素以及它们的下标,多用于在for循环中得到计数,enumerate参数为可遍历的变量，如 字符串，列表等
>>> i=0
>>> seq=['one','two','three']
>>> for element in seq:
... print i, seq
... i +=1
...
0 one
1 two
2 three
>>> seq=['one','two','three']
>>> for i, element in enumerate(seq):
... print i, seq
...
0 one
1 two
2 three
>>> for i,j in enumerate('abcdef'):
... print i,j
...
0 a
1 b
2 c
3 d
4 e
5 f
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