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  1. Apache Arrow
  2. ARROW-1976

[Python] Handling unicode pandas columns on parquet.read_table

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      Description

      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

      import numpy as np
      import pandas as pd
      import pyarrow as pa
      import pyarrow.parquet as pq
      
      df = pd.read_csv('college_data.csv')
      

      For verification, the DataFrame's columns are indeed unicode

      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)
      

      The DataFrame can be saved into a parquet file

      arrow_table = pa.Table.from_pandas(df)
      pq.write_table(arrow_table, 'college_data.parquet')
      

      But trying to read the parquet file immediately afterwards results in the following

      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)
      

      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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              • Assignee:
                Licht-T Licht Takeuchi
                Reporter:
                simbanyatsanga Simbarashe Nyatsanga
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                • Created:
                  Updated:
                  Resolved: