Incorrect docs for mimetypes.MimeTypes.types_map

[maxnikulin]

cpython/Doc/library/mimetypes.rst

Lines 213 to 218 in 13eb521

	.. attribute:: MimeTypes.types_map
	Tuple containing two dictionaries, mapping filename extensions to MIME types:
	the first dictionary is for the non-standards types and the second one is for
	the standard types. They are initialized by :data:`common_types` and
	:data:`types_map`.

Notice

They are initialized by common_types and types_map.

The same is applicable for MimeTypes.types_map_inv. Try

import mimetypes

mimetypes.init()
mimetypes.types_map[".ae1"] = "application/pers.added"
db = mimetypes.MimeTypes()
print(db.types_map[True].get(".ae1"))

it reports

None

Accordingly to the docs I would expect application/pers.added. It can be achieved by commenting out the mimetypes.init() call.

I think, behavior changed when #49213 was fixed, but docs have not been updated.

I see some reason in the documented behavior. Perhaps mimetypes.init() should be more flexible and support both ways to set types_map: from the global dictionary and from the internal data, but likely it should be discussed on the pyhton-ideas mailing list first.

Linked PRs

• gh-115075: Clarify docs for types_map and types_map_inv on mimetypes.MimeTypes #136761
• gh-115075: Fix info about initialization of mimetypes.MimeTypes attributes #150691

[serhiy-storchaka]

This behavior was so long, that it is now considered a new norm. We should just document it. Any changes of the behavior should be considered a new feature.