Python using enumerate inside list comprehension

2019-01-07 02:43发布

Lets suppose I have a list like this:

mylist = ["a","b","c","d"]

To get the values printed along with their index I can use Python's enumerate function like this

>>> for i,j in enumerate(mylist):
...     print i,j
...
0 a
1 b
2 c
3 d
>>>

Now, when I try to use it inside a list comprehension it gives me this error

>>> [i,j for i,j in enumerate(mylist)]
  File "<stdin>", line 1
    [i,j for i,j in enumerate(mylist)]
           ^
SyntaxError: invalid syntax

So, my question is: what is the correct way of using enumerate inside list comprehension?

7条回答
手持菜刀,她持情操
2楼-- · 2019-01-07 03:36

Here's a way to do it:

>>> mylist = ['a', 'b', 'c', 'd']
>>> [item for item in enumerate(mylist)]
[(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd')]

Alternatively, you can do:

>>> [(i, j) for i, j in enumerate(mylist)]
[(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd')]

The reason you got an error was that you were missing the () around i and j to make it a tuple.

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