API: rename pandas/core/generic.py -> pandas/core.ndframe.py

[topper-123]

IMO generic.py is a very anonymous name and it would be better to have the more descriptive name ndframe.py.

core/generic.py will still exist, but will emits a deprecation warning if used/imported from. I've added a deprecation test in pandas/tests/ndframe/test_frame_and_series.py.

[MarcoGorelli]

is pandas.core.generic user-facing? if not, then this will complicate looking through histories of lines (e.g. with git log -G)

[phofl]

We can't do this right now, core is only semi private.

If we want to change things here, we have to deprecate and make it private first

[topper-123]

Hm, yeah, I thought renamed files maintain their git history, but it looks like they don't (at least git log -p -- pandas/core/ndframe.py doesn't), so I guess this PR has a bigger trade-off than I thought when I made it.

I guess unless there is agreement to the cost of this change (losing git history) is worth it, I'll have to close the PR again. I'll leave this open for a while for discussion just in case.

[phofl]

Independent of the git history, we can't do this right now.

We would have to deprecate core first before we can move stuff around

[topper-123]

Actually as I suspected, git history is actually preserved and you can see the git history by using the --followparameter, e.g. git log -p --follow HEAD~100..HEAD -- pandas/core/ndframe.py. OF course, people may forget/not know about --follow, so there's that negative aspect.

@phofl, my plan is to make two PRs in order to maintain git history AND go through a proper deprecation cycle, so this change could be backward compatible as per our normal rules. I've upload the second PR in order to show what I planned (see #51173). If you look at these two PRs as a whole, you'll see it is backward compatible (i.e. the pandas.core.generic is deprecated) and git history is preserved (using --follow).

[phofl]

I am -1 as is.

The general idea is to deprecate core as a whole, technically it is already considered private (https://pandas.pydata.org/docs/reference/index.html)

There is already an open issue about it with lots of discussion:
#27522

Renaming the file and pointing downstream libraries/users to another file when we might want to deprecate the whole module is not a good idea. A bad name is not a strong enough reason to cause all these disturbances and confusing side effects imo.

[topper-123]

Ok no worries, I'll close the PRs. I can see that the core` discussion superceeds this issue.

[topper-123]

Closing based on comments.

[phofl]

Happy to rename generally, but we have to make a decision for the core deprecation first