The problem appears to be that every zipimporter instance keeps its own reference to the zip files table of contents (self->files) instead of continually using the module wide zip_directory_cache but the zip_stat_cache is being maintained externally to that in a module wide fashion.

"import foo.bar" causes an "import foo" followed by an "import foo.bar" which uses a different zipimporter instance.  if it already exists, it's own self->files reference will be out of date despite the module global zip_stat_cache having been updated to say the TOC has been reread.

One solution to this would be to get rid of struct _zipimporter.files entirely and always use zip_directory_cache[self->archive] as the canonical single source for that.

"pro-tip" for anyone working on Python importers: You don't know how import works. Multiple instances of your importers will exist. If you think you know how import works, see the first statement again.