[GitHub] [arrow] jorisvandenbossche commented on pull request #7349: ARROW-8766: [Python] Allow implementing filesystems in Python

[GitBox <gi...@apache.org>]

jorisvandenbossche commented on pull request #7349:
URL: https://github.com/apache/arrow/pull/7349#issuecomment-639062788


   A first test case is working, using fsspec's in-memory filesystem:
   
   ```
   In [1]: import pyarrow.parquet as pq
      ...: import pyarrow.dataset as ds
      ...:
      ...: from pyarrow.fs import PyFileSystem
      ...: from pyarrow.tests.test_fs import FSSpecHandler
   
   In [2]: import fsspec
   
   In [3]: memfs = fsspec.filesystem("memory")
   
   In [4]: table = pa.table({'a': [1, 2, 3]})
   
   In [5]: with memfs.open("test", "wb") as f:
      ...:     pq.write_table(table, f)
      ...:
   
   In [6]: dataset = ds.dataset("test", filesystem=PyFileSystem(FSSpecHandler(memfs)))
   
   In [7]: dataset.to_table(filter=ds.field('a') > 1).to_pandas()
   Out[7]:
      a
   0  2
   1  3
   ```
   
   I only have a bit trouble finding a robust way to get a file handle for an open file from the fsspec filesystem, but so that is not related to this PR ;) For the rest it was quite easy to get this working!


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