Python3内置函数enumerate()

enumerate()是Python的内置函数。

 1 help(enumerate) 2 Help on class enumerate in module builtins: 3 class enumerate(object) 4   enumerate(iterable[, start]) -> iterator for index, value of iterable 5   #enumerate(可迭代变量[,开始下标])->返回迭代变量的索引和值。  （注意，字典和集合也能使用，取位置作为索引） 6   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. 7 enumerate is useful for obtaining an indexed list:  8       (0, seq[0]), (1, seq[1]), (2, seq[2]), ... 9  10  Methods defined here:11   12 __getattribute__(self, name, /)13       Return getattr(self, name).14   15 __iter__(self, /)16       Implement iter(self).17   18 __new__(*args, **kwargs) from builtins.type19      Create and return a new object.  See help(type) for accurate signature.20 21 __next__(self, /)22      Implement next(self).23  24 __reduce__(...)25     Return state information for pickling.

对于一个可迭代的iterable/可遍历的对象（如列表，字符串，元组，字典和集合）。

enumerate()多用于在for循环中得到计数；enumerate()返回的是一个enumerate对象。

 1 for i in enumerate([1,2,3,4,5]):  #对列表作用 2     print(i) 3      4 (0, 1) 5 (1, 2) 6 (2, 3) 7 (3, 4) 8 (4, 5) 9 10 for i in enumerate((1,2,3)): #对元组作用11     print(i)12     13 (0, 1)14 (1, 2)15 (2, 3)16 17 for i in enumerate('help'): #对字符串作用18     print(i)19     20 (0, 'h')21 (1, 'e')22 (2, 'l')23 (3, 'p')24 25 for i in enumerate({'name':'zoe','age':18}):  #对字典作用26     print(i)27     28 (0, 'name')29 (1, 'age')30 31 for i in enumerate({12,3}): #对元组作用32     print(i)33     34 (0, 3)35 (1, 12)