h5(またはfeather) ファイルとして保存したい大きな Pandas データフレーム (~15GB、83m 行) があります。1 つの列には、文字列/オブジェクト型である必要がある、数字の長い ID 文字列が含まれています。しかし、パンダがすべての列を次のように解析することを確認したとしてもobject:
df = pd.read_csv('data.csv', dtype=object)
print(df.dtypes) # sanity check
df.to_hdf('df.h5', 'df')
> client_id object
event_id object
account_id object
session_id object
event_timestamp object
# etc...
次のエラーが表示されます。
File "foo.py", line 14, in <module>
df.to_hdf('df.h5', 'df')
File "/shared_directory/projects/env/lib/python3.6/site-packages/pandas/core/generic.py", line 1996, in to_hdf
return pytables.to_hdf(path_or_buf, key, self, **kwargs)
File "/shared_directory/projects/env/lib/python3.6/site-packages/pandas/io/pytables.py", line 279, in to_hdf
f(store)
File "/shared_directory/projects/env/lib/python3.6/site-packages/pandas/io/pytables.py", line 273, in <lambda>
f = lambda store: store.put(key, value, **kwargs)
File "/shared_directory/projects/env/lib/python3.6/site-packages/pandas/io/pytables.py", line 890, in put
self._write_to_group(key, value, append=append, **kwargs)
File "/shared_directory/projects/env/lib/python3.6/site-packages/pandas/io/pytables.py", line 1367, in _write_to_group
s.write(obj=value, append=append, complib=complib, **kwargs)
File "/shared_directory/projects/env/lib/python3.6/site-packages/pandas/io/pytables.py", line 2963, in write
self.write_array('block%d_values' % i, blk.values, items=blk_items)
File "/shared_directory/projects/env/lib/python3.6/site-packages/pandas/io/pytables.py", line 2730, in write_array
vlarr.append(value)
File "/shared_directory/projects/env/lib/python3.6/site-packages/tables/vlarray.py", line 547, in append
self._append(nparr, nobjects)
File "tables/hdf5extension.pyx", line 2032, in tables.hdf5extension.VLArray._append
OverflowError: value too large to convert to int
とにかくこれを int に変換しようとして失敗しているようです。
実行df.to_feather()時に同様の問題があります：
df.to_feather('df.feather')
File "/shared_directory/projects/env/lib/python3.6/site-packages/pandas/core/frame.py", line 1892, in to_feather
to_feather(self, fname)
File "/shared_directory/projects/env/lib/python3.6/site-packages/pandas/io/feather_format.py", line 83, in to_feather
feather.write_dataframe(df, path)
File "/shared_directory/projects/env/lib/python3.6/site-packages/pyarrow/feather.py", line 182, in write_feather
writer.write(df)
File "/shared_directory/projects/env/lib/python3.6/site-packages/pyarrow/feather.py", line 93, in write
table = Table.from_pandas(df, preserve_index=False)
File "pyarrow/table.pxi", line 1174, in pyarrow.lib.Table.from_pandas
File "/shared_directory/projects/env/lib/python3.6/site-packages/pyarrow/pandas_compat.py", line 501, in dataframe_to_arrays
convert_fields))
File "/usr/lib/python3.6/concurrent/futures/_base.py", line 586, in result_iterator
yield fs.pop().result()
File "/usr/lib/python3.6/concurrent/futures/_base.py", line 425, in result
return self.__get_result()
File "/usr/lib/python3.6/concurrent/futures/_base.py", line 384, in __get_result
raise self._exception
File "/usr/lib/python3.6/concurrent/futures/thread.py", line 56, in run
result = self.fn(*self.args, **self.kwargs)
File "/shared_directory/projects/env/lib/python3.6/site-packages/pyarrow/pandas_compat.py", line 487, in convert_column
raise e
File "/shared_directory/projects/env/lib/python3.6/site-packages/pyarrow/pandas_compat.py", line 481, in convert_column
result = pa.array(col, type=type_, from_pandas=True, safe=safe)
File "pyarrow/array.pxi", line 191, in pyarrow.lib.array
File "pyarrow/array.pxi", line 78, in pyarrow.lib._ndarray_to_array
File "pyarrow/error.pxi", line 85, in pyarrow.lib.check_status
pyarrow.lib.ArrowInvalid: ('Could not convert 1542852887489 with type str: tried to convert to double', 'Conversion failed for column session_id with type object')
そう：
- 数値のように見えるものは、ストレージ内で強制的に数値に変換されていますか?
- NaN の存在は、ここで起こっていることに影響を与える可能性がありますか?
- 代替のストレージ ソリューションはありますか? 何が最高でしょうか？