Change win32InstalledFonts return value

[timhoffm]

PR Summary

In the context of #12173 it was noted that matplotlib.font_manager.win32InstalledFonts() returned None if no fonts are found. This is inconsistent with the docs which claims that a list of fonts is returned. This PR changes the return value to an empty list, which is a more natural choice and is more convenient than the None value. If the value can be None, we have to explicitly check before doing any list-operations on the return value. An empty list can be handled more gracefully.

Returning an empty list is also the behavior of OSXInstalledFonts().

This is in principle a breaking API change. However, I think it's ok to document it and apply it right away.

Note: this fixes one of the exceptions in #12173:

  File "C:\Python\Python35\lib\site-packages\matplotlib\font_manager.py", line 264, in findSystemFonts
    fontfiles.update(win32InstalledFonts(fontext=fontext))
TypeError: 'NoneType' object is not iterable

PR Checklist

• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way

[Kojoley]

There is already #12174, however it did not add an api change entry.

[timhoffm]

Oh, didn't see #12174. The discussion there has gone a bit off-topic as well.

Anyway, we should add an API change note. While it's unlikely that someone will actually use that function and have a problem with the change, it's still a function that appears in the official docs.

[timhoffm]

Taking up the solution proposed by @Kojoley in #12173 (comment)

[Lyghtning]

I don't know if this is allowed or not, I'm a complete novice when it comes to Python, and libraries, imports. What I can say is I had this problem, ended up here after having to do an environment reload which updated my matplotlib.

You guys are amazing, checked out the file update, made the modifications, back up and running.
Thank you for being such contributor to newbies like me. Thank you seriously.

[sebbosafened]

The solution proposed by @Kojoley in #12173 did not solve the issue for me, I still get

 File "C:\Users\thisuser\AppData\Local\Programs\Python\Python35\lib\site-packages\matplotlib\font_manager.py", line 264, in findSystemFonts
    fontfiles.update(win32InstalledFonts(fontext=fontext))
TypeError: 'NoneType' object is not iterable

[Kojoley]

@sebbosafened Hm, I do not know how it is even possible to get a None value after the PR.

line 264

Please, check twice, the line number should be different.

matplotlib/lib/matplotlib/font_manager.py

Line 261 in deae70a

fontfiles.update(win32InstalledFonts(fontext=fontext))

[sebbosafened]

I copied everything from your version of font_manager.py (

matplotlib/lib/matplotlib/font_manager.py

Line 261 in deae70a

fontfiles.update(win32InstalledFonts(fontext=fontext))

) to my local font_manager.py (after backing up my local version that I had already edited - with obvious mistakes - according to yourt post @Kojoley on 23rd september, 00:16 CEST) and now it works. Thank you a lot.

[zunction]

I copied everything from your version of font_manager.py (

matplotlib/lib/matplotlib/font_manager.py

Line 261 in deae70a

fontfiles.update(win32InstalledFonts(fontext=fontext))
) to my local font_manager.py (after backing up my local version that I had already edited - with obvious mistakes - according to yourt post @Kojoley on 23rd september, 00:16 CEST) and now it works. Thank you a lot.

Somehow the contents of font_manager.py have to be manually updated like what @sebbosafened did. I also managed to get it to work after updating my local version of font_manager.py to the version here. Thanks a lot for solving the problem 👍

[AndrewPanB]

I copied everything from your version of font_manager.py (
matplotlib/lib/matplotlib/font_manager.py
Line 261 in deae70a
fontfiles.update(win32InstalledFonts(fontext=fontext))
) to my local font_manager.py (after backing up my local version that I had already edited - with obvious mistakes - according to yourt post @Kojoley on 23rd september, 00:16 CEST) and now it works. Thank you a lot.

Somehow the contents of font_manager.py have to be manually updated like what @sebbosafened did. I also managed to get it to work after updating my local version of font_manager.py to the version here. Thanks a lot for solving the problem

I change "if sys.platform == 'win32:" to if sys.platform == 'win64': in matplotlib/lib/matplotlib/font_manager.py
It works.

[Kojoley]

I change "if sys.platform == 'win32:" to if sys.platform == 'win64': in matplotlib/lib/matplotlib/font_manager.py

It cannot has that value https://mail.python.org/pipermail/patches/2000-May/000648.html
https://github.com/python/cpython/blob/c510c6b8b60f211793e0b84c317ea6974e8a6153/PC/pyconfig.h#L297-L301

[jckling]

I copied everything from your version of font_manager.py (
matplotlib/lib/matplotlib/font_manager.py
Line 261 in deae70a
fontfiles.update(win32InstalledFonts(fontext=fontext))
) to my local font_manager.py (after backing up my local version that I had already edited - with obvious mistakes - according to yourt post @Kojoley on 23rd september, 00:16 CEST) and now it works. Thank you a lot.

Somehow the contents of font_manager.py have to be manually updated like what @sebbosafened did. I also managed to get it to work after updating my local version of font_manager.py to the version here. Thanks a lot for solving the problem

I change "if sys.platform == 'win32:" to if sys.platform == 'win64': in matplotlib/lib/matplotlib/font_manager.py
It works.

It works for me! Thanks a lot 🎉🎉🎉