[jira] [Created] (ARROW-2683) Resource Warning (Unclosed File) when using pyarrow.parquet.read_table()

["Aldrin (JIRA)" <ji...@apache.org>]

Aldrin created ARROW-2683:
-----------------------------

             Summary: Resource Warning (Unclosed File) when using pyarrow.parquet.read_table()
                 Key: ARROW-2683
                 URL: https://issues.apache.org/jira/browse/ARROW-2683
             Project: Apache Arrow
          Issue Type: Bug
          Components: Python
    Affects Versions: 0.9.0
            Reporter: Aldrin


pyarrow version from python repl:
{noformat}
>>> import pyarrow
>>> pyarrow.__version__
'0.9.0.post1'{noformat}
python interpreter information:
{noformat}
Python 3.6.5 (default, Mar 30 2018, 06:42:10)
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.39.2)] on darwin{noformat}
arbitrary, potentially relevant system information:
{noformat}
OS                       : macOS High Sierra (10.13.4)
homebrew package         : python: stable 3.6.5 (bottled), devel 3.7.0b4, HEAD
pip version              : pip 10.0.1
pipenv version           : pipenv, version 2018.05.18
pyarrow version (via pip): pyarrow         0.9.0.post1
cython version (via pip) : Cython          0.28.2{noformat}
 

Issue Description:

I see a ResourceWarning, which doesn't seem to be an error, but seems important enough (a.k.a. annoying enough) that I thought it would be worth asking about. [~xhochy] was nice enough to respond in  #general in the arrow slack.

The main problem is as follows:

# with this code in a python unittest:
{noformat}
def test_arrow_from_parquet(self):
table = parquet.read_table(<path as str>){noformat}
I see this warning:
{noformat}
ResourceWarning: unclosed file <_io.BufferedReader name=<path_to_file>{noformat}
# I tried adding the following, per Uwe's request:
{noformat}
warnings.simplefilter("error"){noformat}
# I then see this information:
{noformat}
test_arrow_from_parquet (tests.datalayer_test.TestFileReader) ... Exception ignored in: <_io.FileIO name=<path_to_file> mode='rb' closefd=True>

ResourceWarning: unclosed file <_io.BufferedReader name=<path_to_file>>{noformat}
# Uwe's thoughts:
{noformat}
That could be a valid error. We don’t seem to close the file we open in `ParquetFile.__init__`{noformat}
 



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