How do I annotate types in a for-loop

问题

I want to annotate a type of a variable in a for-loop. I tried this:

for i: int in range(5):
    pass

But it didn't work, obviously.

What I expect is working autocomplete in PyCharm 2016.3.2. Pre-annotation like this:

i: int
for i in range(5):
    pass

doesn't help.

P.S. Pre-annotation works for PyCharm >= 2017.1

回答1:

According to PEP 526, this is not allowed:

In addition, one cannot annotate variables used in a for or with statement; they can be annotated ahead of time, in a similar manner to tuple unpacking

Annotate it before the loop:

i: int
for i in range(5):
    pass

---

PyCharm 2018.1 and up now recognizes the type of the variable inside the loop. This was not supported in older PyCharm versions.

回答2:

I don't know if this solution is PEP compatible or just a feature of PyCharm but I made it work like this

for i in range(5): #type: int
  pass

and I'm using Pycharm Community Edition 2016.2.1

回答3:

This works well for my in PyCharm (using Python 3.6)

for i in range(5):
    i: int = i
    pass

回答4:

None of the responses here were useful, except to say that you can't. Even the accepted answer uses syntax from the PEP 526 document, which isn't valid python syntax. If you try to type in

x: int

You'll see it's a syntax error.

Here is a useful workaround:

for __x in range(5):
    x = __x  # type: int
    print(x)

Do your work with x. PyCharm recognizes its type, and autocomplete works.

来源：https://stackoverflow.com/questions/41641449/how-do-i-annotate-types-in-a-for-loop