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https://issues.apache.org/jira/browse/ARROW-1743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16223499#comment-16223499
]
ASF GitHub Bot commented on ARROW-1743:
---------------------------------------
Licht-T commented on a change in pull request #1260: ARROW-1743: [Python] Avoid
non-array writeable-flag check
URL: https://github.com/apache/arrow/pull/1260#discussion_r147553977
##########
File path: python/pyarrow/pandas_compat.py
##########
@@ -404,7 +404,7 @@ def table_to_blockmanager(options, table, memory_pool,
nthreads=1):
index_name = None if is_unnamed_index_level(name) else name
col_pandas = col.to_pandas()
values = col_pandas.values
- if not values.flags.writeable:
+ if hasattr(values, 'flags') and not values.flags.writeable:
Review comment:
@xhochy Do we need to check writability of `Categorical.codes` and
`Categorical. categories.values` even if we cannot edit directly?
```python
>>> import pandas as pd
>>> import numpy as np
>>> values = pd.Categorical(['A', 'A'])
>>>
>>> arr = pa.DictionaryArray.from_arrays(
... np.array([0, 0]),
... np.array([100]))
>>>
>>> result = arr.to_pandas()
>>>
>>> result.codes = 1
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python2.7/site-packages/pandas/core/categorical.py",
line 506, in _set_codes
raise ValueError("cannot set Categorical codes directly")
ValueError: cannot set Categorical codes directly
>>>
>>> result.categories.values = 1
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: can't set attribute
```
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> Table to_pandas fails when index contains categorical column
> ------------------------------------------------------------
>
> Key: ARROW-1743
> URL: https://issues.apache.org/jira/browse/ARROW-1743
> Project: Apache Arrow
> Issue Type: Bug
> Components: Python
> Affects Versions: 0.7.1
> Reporter: Brian Pendleton
> Assignee: Licht Takeuchi
> Labels: pull-request-available
>
> Categorical columns in the index of a dataframe are causing a roundtrip
> failure.
> {code}
> >>> df = pd.DataFrame({'a': [1, 2, 3], 'b': [1, 2, 3]})
> >>> df['a'] = df.a.astype('category')
> >>> df = df.set_index('a')
> >>> tbl = pa.Table.from_pandas(df)
> >>> tbl.to_pandas()
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> File "table.pxi", line 881, in pyarrow.lib.Table.to_pandas
> File
> "C:\Users\bpendlet\Miniconda3\envs\panpy3\lib\site-packages\pyarrow\pandas_compat.py",
> line 303, in table_to_blockmanager
> if not values.flags.writeable:
> AttributeError: 'Categorical' object has no attribute 'flags'
> {code}
> Works as expected when you don't change have the categorical:
> {code}
> >>> df = pd.DataFrame({'a': [1, 2, 3], 'b': [1, 2, 3]})
> >>> df = df.set_index('a')
> >>> tbl = pa.Table.from_pandas(df)
> >>> tbl.to_pandas()
> b
> a
> 1 1
> 2 2
> 3 3
> {code}
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