python中enumerate用法

enumerate()

A new built-in function, enumerate()
, will make certain loops a bit clearer. enumerate(thing)
, where thing
is either an iterator or a sequence, returns a iterator that will return (0, thing
[0])
, (1, thing
[1])
, (2, thing
[2])
, and so forth.

A common idiom to change every element of a list looks like this:

 

for i in range(len(L)):
    item = L[i]
    # ... compute some result based on item ...
    L[i] = result

This can be rewritten using enumerate()
as:

 

for i, item in enumerate(L):
    # ... compute some result based on item ...
    L[i] = result


example:

#!/usr/bin/env python
string = 'mytest'

for i in range(len(string)):
    print string[i],'(%d)' %i


for i,item in enumerate(string):
    print item,'(%d)' %i