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https://issues.apache.org/jira/browse/ARROW-1976?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16318720#comment-16318720
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Phillip Cloud commented on ARROW-1976:
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Note this is python 2 specific. You won't run into issues like this if you
don't use python 2.
If there's no restriction on the version of Python you need to use please use
python 3.
That said, since we have to support python 2, this is a bug.
How is it possible to read in Unicode from a CSV file without specifying an
encoding to {{read_csv}}? Pandas must make an assumption about the encoding or
choose a default.
I've also submitted a data issue to data.gov to request that they include the
encoding in the metadata.
https://www.data.gov/issue/request-id/635154
> Handling unicode pandas columns on pq.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
>
> 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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