In typing docs, note explicit import needed for IO and Pattern/Match

[KarlKornel]

BPO	38352
Nosy	@gvanrossum, @doerwalter, @ambv, @ilevkivskyi, @JelleZijlstra, @pablogsal, @miss-islington
PRs	bpo-38352: Add to typing.__all__ #25821 [3.10] bpo-38352: Add to typing.__all__ (GH-25821) #25884 [3.9] bpo-38352: Add to typing.__all__ (GH-25821) #25885

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2021-05-04.10:08:56.605>
created_at = <Date 2019-10-02.18:31:17.565>
labels = ['3.11', 'type-bug', '3.9', '3.10', 'docs']
title = 'In typing docs, note explicit import needed for IO and Pattern/Match'
updated_at = <Date 2021-07-18.15:30:54.926>
user = 'https://bugs.python.org/KarlKornel'

bugs.python.org fields:

activity = <Date 2021-07-18.15:30:54.926>
actor = 'pablogsal'
assignee = 'docs@python'
closed = True
closed_date = <Date 2021-05-04.10:08:56.605>
closer = 'lukasz.langa'
components = ['Documentation']
creation = <Date 2019-10-02.18:31:17.565>
creator = 'Karl Kornel'
dependencies = []
files = []
hgrepos = []
issue_num = 38352
keywords = ['patch']
message_count = 9.0
messages = ['353763', '353917', '382497', '382500', '392731', '392868', '392869', '392870', '392894']
nosy_count = 9.0
nosy_names = ['gvanrossum', 'doerwalter', 'docs@python', 'lukasz.langa', 'levkivskyi', 'JelleZijlstra', 'pablogsal', 'Karl Kornel', 'miss-islington']
pr_nums = ['25821', '25884', '25885']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue38352'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

[KarlKornel]

Hello!

In https://github.com/python/cpython/blob/master/Lib/typing.py#L115-L117, there is a note about the io and re classes not being included in typing.all. I am a relatively new user of typing, and I did from typing import * in my code. I ran the code through mypy first, which reported no problems, but then running Python 3.6 failed with a NameError (name 'IO' is not defined).

Reading through the typing source, it's clear that this was an intentional decision. So, instead of reporting a bug, I'd like to request a documentation enhancement!

The docs for typing make no mention of typing.io or typing.re. So, my request is: In the sections for the IO/TextIO/BinaryIO and Pattern/Match classes, include text warning the user that these types are not imported when you do from typing import *.

[ilevkivskyi]

So, my request is: In the sections for the IO/TextIO/BinaryIO and Pattern/Match classes, include text warning the user that these types are not imported when you do from typing import *.

I don't think this should really be a warning, probably just a note, but otherwise I totally agree. Would you like to make a PR?

[doerwalter]

Shadowing the real modules re and io by

   from typing import *

would indeed be bad, but that argument IMHO doesn't hold for the types IO, TextIO and BinaryIO, yet they are not listed in typing.__all__. Is there a reason for that? And if not, could IO, TextIO and BinaryIO be added to typing.__all__?

[gvanrossum]

Wait, is the OP maybe that there’s a difference between typeshed an the stdlib typing.py?

[JelleZijlstra]

It turns out that IO, TextIO, BinaryIO, Match, and Pattern aren't in typing.__all__. As Walter points out above, there's no clear reason for this. I am submitting a PR to add them to __all__.

[ambv]

New changeset e1bcc88 by Miss Islington (bot) in branch '3.10':
bpo-38352: Add to typing.__all__ (GH-25821) (bpo-25884)
e1bcc88

[ambv]

New changeset 00726e5 by Miss Islington (bot) in branch '3.9':
bpo-38352: Add to typing.__all__ (GH-25821) (bpo-25885)
00726e5

[ambv]

Fix merged to main (3.11), 3.10, and 3.9. Not applicable to older Pythons as they are security fixes only.

[JelleZijlstra]

@Łukasz thanks for your merging spree!

I'm actually not sure this should go into 3.9. Seems potentially dangerous that people upgrading from an earlier 3.9 patch release will now see new names injected into their namespace if they do from typing import *.