title: Pyarrow: TypeError: an integer is required (got type str)
body: <p>I have a dataframe with following dtype:</p>
  <pre><code>[2020-02-06 19:15:06,579] {logging_mixin.py:95} INFO - 
  campanha                      object
  chave_sistema_origem           int64
  valor_ajustado                object
  </code></pre>
  <p>The column <code>valor_ajustado</code> has some value that is throwing me an exception when I try to write a parquet file using <code>df.to_parquet(buffer, index=False)</code></p>
  <pre><code>[2020-02-06 19:15:06,597] {taskinstance.py:1047} ERROR - an integer is required (got type str)
  ...
    File &quot;/Users/jackhammer/.virtualenvs/python373/lib/python3.7/site-packages/pyarrow/pandas_compat.py&quot;, line 540, in convert_column
      result = pa.array(col, type=type_, from_pandas=True, safe=safe)
    File &quot;pyarrow/array.pxi&quot;, line 207, in pyarrow.lib.array
    File &quot;pyarrow/array.pxi&quot;, line 78, in pyarrow.lib._ndarray_to_array
  </code></pre>
  <p>I know that column <code>valor_ajustado</code> has values like:</p>
  <blockquote>
  <p>0</p>
  <p>123,48</p>
  <p>1</p>
  <p>493,987</p>
  </blockquote>
  <p>Anyone knows why it's trying to manipulate integers instead of keep column as an object?</p>