list_3 = []
list_1 = ['2', '5', '6', '11', '2', '535', '2', '2' ]
print(list_1)
s = '2'
for item in enumerate(list_1):
    if item[1] == str(s):
        list_3.append(item[0])
print(list_3)

執行結果：

['2', '5', '6', '11', '2', '535', '2', '2']
[0, 4, 6, 7]

列舉：

for i in enumerate(('a','b
 
','c')):
    print (i)

(0, 'a')
(1, 'b')
(2, 'c')

for i,j in enumerate(('a','b','c')):
    print (i,j)

執行結果：

0 a
1 b
2 c