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)