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https://issues.apache.org/jira/browse/ARROW-1976?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16350401#comment-16350401
]
ASF GitHub Bot commented on ARROW-1976:
---------------------------------------
simnyatsanga commented on issue #1476: ARROW-1976: [Python] Fix Pandas data
SerDe with Unicode column names in Python 2.7
URL: https://github.com/apache/arrow/pull/1476#issuecomment-362601973
I'm looking at getting the failing tests to pass. Specifically one of the
failing tests looks like this
https://github.com/apache/arrow/blob/master/python/pyarrow/tests/test_convert_pandas.py#L141
```
def test_multiindex_columns(self):
columns = pd.MultiIndex.from_arrays([
['one', 'two'], ['X', 'Y']
])
df = pd.DataFrame([(1, 'a'), (2, 'b'), (3, 'c')], columns=columns)
_check_pandas_roundtrip(df, preserve_index=True)
```
The pandas roundtrip is failing in this branch on this line:
https://github.com/apache/arrow/blob/master/python/pyarrow/pandas_compat.py#L166
Because the `column_name` (which is part of a MultiIndex) is coming in as a
tuple instead of a string. On master the `column_name` is indeed coming in as a
string. I'm trying to figure out, what changes on this branch would cause this.
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> [Python] Handling unicode pandas columns on parquet.read_table
> --------------------------------------------------------------
>
> Key: ARROW-1976
> URL: https://issues.apache.org/jira/browse/ARROW-1976
> Project: Apache Arrow
> Issue Type: Bug
> Components: Python
> Affects Versions: 0.8.0
> Reporter: Simbarashe Nyatsanga
> Assignee: Licht Takeuchi
> Priority: Major
> Labels: pull-request-available
> Fix For: 0.9.0
>
>
> Unicode columns in pandas DataFrames aren't being handled correctly for some
> datasets when reading a parquet file into a pandas DataFrame, leading to the
> common Python ASCII encoding error.
>
> The dataset used to get the error is here:
> https://catalog.data.gov/dataset/college-scorecard
> {code}
> import numpy as np
> import pandas as pd
> import pyarrow as pa
> import pyarrow.parquet as pq
> df = pd.read_csv('college_data.csv')
> {code}
> For verification, the DataFrame's columns are indeed unicode
> {code}
> df.columns
> > Index([u'UNITID', u'OPEID', u'OPEID6', u'INSTNM', u'CITY', u'STABBR',
> u'INSTURL', u'NPCURL', u'HCM2', u'PREDDEG',
> ...
> u'RET_PTL4', u'PCTFLOAN', u'UG25ABV', u'MD_EARN_WNE_P10', u'GT_25K_P6',
> u'GRAD_DEBT_MDN_SUPP', u'GRAD_DEBT_MDN10YR_SUPP', u'RPY_3YR_RT_SUPP',
> u'C150_L4_POOLED_SUPP', u'C150_4_POOLED_SUPP'],
> dtype='object', length=123)
> {code}
> The DataFrame can be saved into a parquet file
> {code}
> arrow_table = pa.Table.from_pandas(df)
> pq.write_table(arrow_table, 'college_data.parquet')
> {code}
> But trying to read the parquet file immediately afterwards results in the
> following
> {code}
> df = pq.read_table('college_data.parquet').to_pandas()
> > ---------------------------------------------------------------------------
> UnicodeEncodeError Traceback (most recent call last)
> <ipython-input-29-23906ea1efe3> in <module>()
> ----> 2 df = pq.read_table('college_data.parquet').to_pandas()
> /Users/anaconda/envs/env/lib/python2.7/site-packages/pyarrow/table.pxi in
> pyarrow.lib.Table.to_pandas
> (/Users/travis/build/BryanCutler/arrow-dist/arrow/python/build/temp.macosx-10.6-intel-2.7/lib.cxx:46331)()
> 1041 if nthreads is None:
> 1042 nthreads = cpu_count()
> -> 1043 mgr = pdcompat.table_to_blockmanager(options, self,
> memory_pool,
> 1044 nthreads)
> 1045 return pd.DataFrame(mgr)
> /Users/anaconda/envs/env/lib/python2.7/site-packages/pyarrow/pandas_compat.pyc
> in table_to_blockmanager(options, table, memory_pool, nthreads, categoricals)
> 539 if columns:
> 540 columns_name_dict = {
> --> 541 c.get('field_name', str(c['name'])): c['name'] for c in
> columns
> 542 }
> 543 columns_values = [
> /Users/anaconda/envs/env/lib/python2.7/site-packages/pyarrow/pandas_compat.pyc
> in <dictcomp>((c,))
> 539 if columns:
> 540 columns_name_dict = {
> --> 541 c.get('field_name', str(c['name'])): c['name'] for c in
> columns
> 542 }
> 543 columns_values = [
> UnicodeEncodeError: 'ascii' codec can't encode character u'\ufeff' in
> position 0: ordinal not in range(128)
> {code}
> Looking at the stacktrace , it looks like this line, which is using str which
> by default will try to do ascii encoding:
> https://github.com/apache/arrow/blob/master/python/pyarrow/pandas_compat.py#L541
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