enumerate函数

enumerate(iterable, start=0)

　　__next__()方法

# 枚举可迭代对象a
a = ['Mary', 'had', 'little']
for i, e in enumerate(a):
    print(i, e)

# 列出枚举对象
seasons = ['Spring', 'Summer', 'Fall', 'Winter']
print(list(enumerate(seasons)))

# 等价函数
def enumerate(sequence, start=0):
    n = start
    for elem in sequence:
        yield n, elem
        n += 1

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　　Loop Methods 循环技巧