Python enumerate 用法

摘要: 偶遇 enumerate 知晓它的奇妙之处

List 迭代时使用索引

使用索引，标准（一般）的做法

array = [1, 2, 3, 4, 5]

for i in range(len(array)):
print(array[i],end=' ')

1 2 3 4 5

简单，干净的用法 ----使用enumerate

enumerate

(iterable, start=0)

Return an enumerate object.

iterable must be a sequence, an iterator, or some other object which supports iteration

start：改变索引 初始化位置（以下有例子）

实例：

>>> seasons = ['Spring', 'Summer', 'Fall', 'Winter']
>>> list(enumerate(seasons))
[(0, 'Spring'), (1, 'Summer'), (2, 'Fall'), (3, 'Winter')]
>>> list(enumerate(seasons, start=1))
[(1, 'Spring'), (2, 'Summer'), (3, 'Fall'), (4, 'Winter')]

完整的用法：

array = [1, 2, 3, 4, 5]  # or whatever

for i, e in enumerate(array):
print(i,e)

0 1
1 2
2 3
3 4
4 5

有start 用法：

for i, e in enumerate(array,start=2):
print(i,e)

2 1
3 2
4 3
5 4
6 5

Equivalent to:

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