python打印列表中指定元素的所有下标

1》法一：
song@ubuntu:~$ vi find2.py
song@ubuntu:~$ more find2.py
l=[1,2,3,4,7,2,5,6,2,8,9,0]
first=0
for i in range(l.count(2)):
    new_l=l[first:]
    index=first+new_l.index(2)
    print 'find the index of 2:',index
    first=index+1

song@ubuntu:~$ python find2.py
find the index of 2: 1
find the index of 2: 5
find the index of 2: 8
song@ubuntu:~$ 

2》法二：
song@ubuntu:~$ vi find_2.py
song@ubuntu:~$ more find_2.py
l=[2,2,3,4,5,1,2,3,1,2,3,4,5]
first=True
for i in range(l.count(2)):
    if first==True:
        pos=l.index(2)
        first=False
    else:
        pos=l.index(2,pos+1)

    print pos

song@ubuntu:~$ python find_2.py
0
1
6
9
song@ubuntu:~$

3》法三：
song@ubuntu:~$ vi find_2_1.py
song@ubuntu:~$ more find_2_1.py
l=[2,2,3,4,5,1,2,3,1,2,3,4,5]
for i in range(len(l)):
    if l[i]==2:

        print i

song@ubuntu:~$ python find_2_1.py
0
1
6
9

song@ubuntu:~$ 

4》法四：

song@ubuntu:~$ vi find_2.py
song@ubuntu:~$ more find_2.py
l=[2,2,3,4,5,1,2,3,1,2,3,4,5]
for i in range(l.count(2)):
    if i==0:
        pos=l.index(2)
    else:
        pos=l.index(2,pos+1)
    print pos
song@ubuntu:~$ python find_2.py
0
1
6
9

5》法五：

song@ubuntu:~$ vi find_2.py
song@ubuntu:~$ more find_2.py
l=[2,2,3,4,5,1,2,3,1,2,3,4,5]
pos=-1
for i in range(l.count(2)):
    pos=l.index(2,pos+1)
    print pos
song@ubuntu:~$ python find_2.py
0
1
6
9

（完）