BUG: Fix regression in is_list_like

[aiudirog]

is_list_like() used to use isinstance(obj, abc.Iterable) before #39852 where it was optimized for performance. This resulted in a regression where objects that explicitly declare __iter__ as None are considered "list like" but not instances of abc.Iterable.

Because the original original PR was focused on performance, here are the same timeit cases run on this PR:

In[1]: import numpy as np
In[2]: from pandas._libs.lib import is_list_like
In[3]: arr = np.array(0)
In[4]: arr2 = np.array([0])

In[5]: %timeit is_list_like([])
51.3 ns ± 0.231 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)  <- master
56.3 ns ± 0.44 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)   <- PR
153 ns ± 2.4 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)     <- isinstance(obj, abc.Iterable)

In[6]: %timeit is_list_like(0)
117 ns ± 2.19 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)    <- master
126 ns ± 2 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)       <- PR
154 ns ± 1.18 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)    <- isinstance(obj, abc.Iterable)

In[7]: %timeit is_list_like(arr)
49.5 ns ± 0.156 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)  <- master
50.6 ns ± 0.14 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)   <- PR
152 ns ± 1.12 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)    <- isinstance(obj, abc.Iterable)

In[8]: %timeit is_list_like(arr2)
50.8 ns ± 1.36 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)   <- master
51.5 ns ± 0.179 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)  <- PR
151 ns ± 0.582 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)   <- isinstance(obj, abc.Iterable)

• tests added / passed
• Ensure all linting tests pass, see here for how to run them
• whatsnew entry

[jreback]

no objection, ping on green (you can add a release not if you'd like), 1.4.

[aiudirog]

no objection, ping on green (you can add a release not if you'd like), 1.4.

Where do you think the best place to put the release note is? doc/sources/whatsnew/v1.4.0rst -> Bug Fixes -> Other?

[jbrockmendel]

Bug Fixes -> Other?

That's fine, yes.

[phofl]

Shouldn't we backport is its a regression?

[jreback]

-0 on backporting. its no big deal to do, but i think this is a very minor case. @phofl do you feel strongly here?

[phofl]

No, just wanted to avoid that it gets missed

[jreback]

ok let's do it.

@aiudirog can you add a note to 1.3.3 regression section.

[aiudirog]

Will do, I'll take care of it later tonight.

[aiudirog]

Issue #42549 is related, but not the same as this issue: is_list_like also fails to detect __getitem__ implemented without __iter__. IMO solving that should require a different PR because it isn't a regression as isinstance(obj, abc.Iterable) doesn't detect those either, explicitly.

[jreback]

thanks @aiudirog

[jreback]

@meeseeksdev backport 1.3.x

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