Python内置函数enumerate()

enumerate()是Python的内置函数。

 help(enumerate)
 Help on class enumerate in module builtins:
 class enumerate(object)
   enumerate(iterable[, start]) -> iterator for index, value of iterable
   #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）
   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[0]), (1, seq[1]), (2, seq[2]), ...

  Methods defined here:

 __getattribute__(self, name, /)
       Return getattr(self, name).

 __iter__(self, /)
       Implement iter(self).

 __new__(*args, **kwargs) from builtins.type
      Create and return a new object.  See help(type) for accurate signature.

 __next__(self, /)
      Implement next(self).

 __reduce__(...)
     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。

 for i in enumerate([1,2,3,4,5]):  #对列表作用
     print(i)

 (0, 1)
 (1, 2)
 (2, 3)
 (3, 4)
 (4, 5)

 for i in enumerate((1,2,3)): #对元组作用
     print(i)

 (0, 1)
 (1, 2)
 (2, 3)

 for i in enumerate('help'): #对字符串作用
     print(i)

 (0, 'h')
 (1, 'e')
 (2, 'l')
 (3, 'p')

 for i in enumerate({'name':'zoe','age':18}):  #对字典作用
     print(i)

 (0, 'name')
 (1, 'age')

 for i in enumerate({12,3}): #对元组作用
     print(i)

 (0, 3)
 (1, 12)