Python标准库-enumerate用法

Posted 2020-10-15

enumerate 枚举

enumerate(iterable, start=0)

Return an enumerate object. iterable 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 iterable.

将一个可支持迭代的对象，转化为枚举， 所以列表，序列，或者其他可迭代的对象即可以；枚举会返回一个包含数字和迭代器中的值的元组；最终返回一个可枚举对象；

典型用法：

　

seasons = [‘Spring‘, ‘Summer‘, ‘Fall‘, ‘Winter‘]

list(enumerate(seasons))

[(0, ‘Spring‘), (1, ‘Summer‘), (2, ‘Fall‘), (3, ‘Winter‘)]

简单实现：

def enumerate(sequence, start=0):
    n = start
    for x in sequence:
        yield n, x
        n += 1