fix(python): Respect dtype and strict in pl.Series's constructor for pyarrow arrays, numpy arrays, and pyarrow-backed pandas

[luke396]

xref #15948 (comment) and a follow-up PR of #15948

Fix wrong dtype when create pl.Series from pd.Series.

when

print(pl.Series("foo", pd.Series([1, 2, 3], dtype='Int64'), pl.Float32))

before

shape: (3,)
Series: 'foo' [i64]
[
	1
	2
	3
]

after

shape: (3,)
Series: 'foo' [f32]
[
	1.0
	2.0
	3.0
]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.98%. Comparing base (acb601d) to head (c000f20).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #15962   +/-   ##
=======================================
  Coverage   80.97%   80.98%           
=======================================
  Files        1386     1386           
  Lines      178479   178479           
  Branches     2877     2877           
=======================================
+ Hits       144530   144539    +9     
+ Misses      33458    33448   -10     
- Partials      491      492    +1     

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[luke396]

Thanks, @MarcoGorelli, for the quick review. I believe I now understand what you meant and have made the necessary changes.

[MarcoGorelli]

Thanks for updating! I think this is very close 💪

I'd just suggest expanding the tests, to include:

• a test where you convert from a pyarrow array with strict=False
• a test where you convert from a pandas series with strict=False

[luke396]

• a test where you convert from a pyarrow array with strict=False
• a test where you convert from a pandas series with strict=False

I believe the change has been made

[MarcoGorelli]

I might be missing something, but I don't see what these tests add to what you already have

Rather than adding these, how about testing converting from a numpy array with [-1, 2, 3] to a Polars Series with dtype pl.UInt8, with strict=False and strict=True? I think this will cover the behaviour change you mentioned in https://github.com/pola-rs/polars/pull/15962/files#r1590912969

[luke396]

The two tests added earlier were because I felt there needed to be a simple test with strict=False without any other parameters. However, I think you are right, these two tests are covered by others.

The behavior change mentioned in #15962 (comment) has been covered by the test using strict=False like below. It was precisely because of your previous suggestion to modify the test that I discovered this potential problem.

s = pl.Series("foo", pd.Series([-1, 2, 3], dtype="Int8"), pl.UInt8, strict=False)
assert s.to_list() == [None, 2, 3]
assert s.dtype == pl.UInt8

Nevertheless, I will add a test with a numpy array and the strict parameter.

[MarcoGorelli]

Nice, thanks @luke396 !

[luke396]

Thanks, @MarcoGorelli, for your patience and selfless help. This PR wouldn't have been completed without you!