import string
a = string.letters
help(int)
b = string.letters
a == b # False

I am unable to reproduce this.

Can you double check that this occurs in the plain Python interpreter or IDLE, and provide a minimum reproducible example? (No third-party IDEs or interpreters, such as Jupyter.)

These guidelines may help:

https://en.wikipedia.org/wiki/Minimal_working_example

http://sscce.org/

https://stackoverflow.com/help/minimal-reproducible-example

I *can* reproduce, on macOS 10.14.6, Python 2.7.17 (from macports).

Python 2.7.17 (default, Oct 20 2019, 14:46:50) 
[GCC 4.2.1 Compatible Apple LLVM 10.0.1 (clang-1001.0.46.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import string
>>> string.letters
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
>>> help(int)  # brings up pager; page through to the end

>>> string.letters
'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'

With 2.7.16 on cygwin, I get:

>>> import string
>>> string.letters
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
>>> help(int)
>>> string.letters
'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'

But given that there's only 2 weeks of support left for 2.7, I don't see this getting changed.

Here's where `string.letters` is reassigned: https://github.com/python/cpython/blob/5f2c1345a79f205c680ed6e0a6ed44199546d79e/Modules/_localemodule.c#L136-L147

That code looks like it's exercised whenever setlocale is (or possibly just when LC_CTYPE is changed). I haven't yet figured out which part of the help machinery causes that.

> But given that there's only 2 weeks of support left for 2.7, I don't see this getting changed.

Agreed: I can't reproduce on Python 3, and it looks as though the offending code is gone from the codebase in Python 3, so this is pretty much just a historical oddity at this point.

For completeness, here's the path leading to the reassignment (after hacking in a raise to the appropriate place in _localemodule.c). It's a side-effect of calling `locale.getpreferredencoding`.

>>> help(int)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/mdickinson/GitHub/python/cpython/Lib/site.py", line 445, in __call__
    import pydoc
  File "/Users/mdickinson/GitHub/python/cpython/Lib/pydoc.py", line 202, in <module>
    _encoding = locale.getpreferredencoding()
  File "/Users/mdickinson/GitHub/python/cpython/Lib/locale.py", line 616, in getpreferredencoding
    setlocale(LC_CTYPE, "")
  File "/Users/mdickinson/GitHub/python/cpython/Lib/locale.py", line 581, in setlocale
    return _setlocale(category, locale)
ValueError: about to reassign string.letters


So a minimal reproducer is something like:

Python 2.7.17 (default, Oct 20 2019, 14:46:50) 
[GCC 4.2.1 Compatible Apple LLVM 10.0.1 (clang-1001.0.46.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import string, locale
>>> string.letters
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
>>> locale.getpreferredencoding()
'UTF-8'
>>> string.letters
'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'

@Zectbumo: is this causing you any practical problem? Or is it just a curiosity?

There's no reasonable way I can see to fix this. The reassignment of those string attributes is clearly intentional (it's even documented) and there's probably code somewhere that relies on it. I think the best we can do is close as "won't fix" though "not a bug" may be more accurate: the code is clearly behaving as intended and designed, even if the design is questionable.

@eric.smith
It actually caused a problem and then turned into a curiosity. At the beginning I wanted to remind myself about the string module so I did a help(string). Then right after that I wrote a program that generated filenames from string.letters. I closed the python interpreter down and then reopened it and regenerated filenames again using string.letters. To my surprise I found the second iteration to come out with completely different results messing up my work. Once I found that help() was causing this problem and it became a curiosity because you would think help() would not modify anything. Obviously this problem is easy to work around in my case.

Since this has been this way for 22 years without a previous report that I can find, +1 to closing as "won't fix"/"not a bug" and so doing.  However, I'm also adding the 2.7 release manager to make sure he knows about it and can reopen if he wants.