CLN: PY3 String/BytesIO

[mroeschke]

• xref CLN: remove PY2 #25725
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff

Imports StringIO and BytesIO from io. Removes cStringIO

[WillAyd]

Minor arguably unrelated request but I think makes sense to address here. Otherwise lgtm

[codecov]

Codecov Report

Merging #25954 into master will decrease coverage by <.01%.
The diff coverage is 91.3%.

@@            Coverage Diff             @@
##           master   #25954      +/-   ##
==========================================
- Coverage   91.82%   91.81%   -0.01%     
==========================================
  Files         175      175              
  Lines       52581    52584       +3     
==========================================
+ Hits        48280    48282       +2     
- Misses       4301     4302       +1

Flag	Coverage Δ
#multiple	90.37% <91.3%> (ø)	⬆️
#single	41.9% <73.91%> (-0.07%)	⬇️

Impacted Files	Coverage Δ
pandas/compat/__init__.py	71.71% <ø> (+1%)	⬆️
pandas/io/formats/format.py	97.89% <100%> (ø)	⬆️
pandas/io/json/json.py	93.24% <100%> (+0.01%)	⬆️
pandas/io/common.py	91.87% <100%> (ø)	⬆️
pandas/io/formats/csvs.py	98.2% <100%> (ø)	⬆️
pandas/core/series.py	93.67% <100%> (ø)	⬆️
pandas/core/computation/expr.py	88.55% <100%> (+0.02%)	⬆️
pandas/core/frame.py	96.79% <100%> (-0.12%)	⬇️
pandas/core/computation/scope.py	93.13% <100%> (+0.06%)	⬆️
pandas/io/clipboards.py	100% <100%> (ø)	⬆️
... and 5 more

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[codecov]

Codecov Report

Merging #25954 into master will decrease coverage by <.01%.
The diff coverage is 92%.

@@            Coverage Diff             @@
##           master   #25954      +/-   ##
==========================================
- Coverage   91.84%   91.84%   -0.01%     
==========================================
  Files         175      175              
  Lines       52553    52552       -1     
==========================================
- Hits        48269    48267       -2     
- Misses       4284     4285       +1

Flag	Coverage Δ
#multiple	90.4% <92%> (ø)	⬆️
#single	41.9% <76%> (-0.07%)	⬇️

Impacted Files	Coverage Δ
pandas/compat/__init__.py	74.43% <ø> (+1.24%)	⬆️
pandas/io/formats/format.py	97.89% <100%> (ø)	⬆️
pandas/io/json/json.py	93.24% <100%> (+0.01%)	⬆️
pandas/io/common.py	91.87% <100%> (ø)	⬆️
pandas/io/formats/csvs.py	98.2% <100%> (ø)	⬆️
pandas/core/series.py	93.67% <100%> (ø)	⬆️
pandas/core/computation/expr.py	88.55% <100%> (+0.02%)	⬆️
pandas/core/frame.py	96.79% <100%> (-0.12%)	⬇️
pandas/core/computation/scope.py	93.13% <100%> (+0.06%)	⬆️
pandas/io/clipboards.py	100% <100%> (ø)	⬆️
... and 8 more

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[mroeschke]

@WillAyd mind helping me interpret these typing errors (not too familiar with mypy)?

pandas/io/common.py:414: error: Definition of "__enter__" in base class "ZipFile" is incompatible with definition in base class "BytesIO"
pandas/io/common.py:414: error: Definition of "__enter__" in base class "ZipFile" is incompatible with definition in base class "BinaryIO"
pandas/io/common.py:414: error: Definition of "__enter__" in base class "ZipFile" is incompatible with definition in base class "IO"
pandas/io/common.py:414: error: Definition of "__exit__" in base class "ZipFile" is incompatible with definition in base class "BytesIO"
pandas/io/common.py:414: error: Definition of "read" in base class "ZipFile" is incompatible with definition in base class "BytesIO"
pandas/io/common.py:414: error: Definition of "read" in base class "ZipFile" is incompatible with definition in base class "IO"
pandas/io/common.py:414: error: Definition of "write" in base class "ZipFile" is incompatible with definition in base class "BytesIO"
pandas/io/common.py:414: error: Definition of "write" in base class "ZipFile" is incompatible with definition in base class "BinaryIO"
pandas/io/common.py:414: error: Definition of "write" in base class "ZipFile" is incompatible with definition in base class "IO"

AFAICT, it has to do with this class defintion

pandas/pandas/io/common.py

Line 414 in f90f4aa

class BytesZipFile(zipfile.ZipFile, BytesIO):

[WillAyd]

Not at a computer to check but I think this happens if a subclass overrides a method with a signature that varies from the parent class. I’ll see what I can dig up

…

Sent from my iPhone

On Apr 2, 2019, at 1:14 PM, Matthew Roeschke ***@***.***> wrote: @WillAyd mind helping me interpret these typing errors (not too familiar with mypy)? pandas/io/common.py:414: error: Definition of "__enter__" in base class "ZipFile" is incompatible with definition in base class "BytesIO" pandas/io/common.py:414: error: Definition of "__enter__" in base class "ZipFile" is incompatible with definition in base class "BinaryIO" pandas/io/common.py:414: error: Definition of "__enter__" in base class "ZipFile" is incompatible with definition in base class "IO" pandas/io/common.py:414: error: Definition of "__exit__" in base class "ZipFile" is incompatible with definition in base class "BytesIO" pandas/io/common.py:414: error: Definition of "read" in base class "ZipFile" is incompatible with definition in base class "BytesIO" pandas/io/common.py:414: error: Definition of "read" in base class "ZipFile" is incompatible with definition in base class "IO" pandas/io/common.py:414: error: Definition of "write" in base class "ZipFile" is incompatible with definition in base class "BytesIO" pandas/io/common.py:414: error: Definition of "write" in base class "ZipFile" is incompatible with definition in base class "BinaryIO" pandas/io/common.py:414: error: Definition of "write" in base class "ZipFile" is incompatible with definition in base class "IO" AFAICT, it has to do with this class defintion https://github.com/pandas-dev/pandas/blob/f90f4aad4589727ebb3235326970a9110aaa309f/pandas/io/common.py#L414 — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

[WillAyd]

So the error messages here are rather explicit; the problem is that with multiple inheritance the two classes that object derives from has conflicting signatures. Here's a related issue on the MyPy tracker:

python/mypy#2125

This code is pretty tricky though - do you see a test case that actually hits this? Actually wondering if multiple inheritance is even required or if it can subclass ZipFile directly, given it's constructor matches that and the call to writestr can accept bytes or str anyway.

If not then ignoring the types might be the only way to go about this

[mroeschke]

Thanks for the tips @WillAyd. Since this PR isn't concerned with typing just ignoring the typing check for the BytesZipFile class.

[jreback]

thanks @mroeschke

@WillAyd its ok to ignore these for now; can circle back later (maybe even add a check to detect types we are ignoring).