Tomas Remes created ARROW-9369:
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Summary: Can't convert dictionary type using table.from_pandas
Key: ARROW-9369
URL: https://issues.apache.org/jira/browse/ARROW-9369
Project: Apache Arrow
Issue Type: Bug
Affects Versions: 0.17.1
Reporter: Tomas Remes
Hello, I am trying to do the following (please correct me if I am doing some
non-sense):
{code:python}
import pandas as pd
import pyarrow as pa
import pyarrow.parquet as pq
fields = [pa.field("object", pa.dictionary(pa.int64(), pa.string()))]
data = {"object": {
"a": "a",
"b": "b",
"c": "c",
"s": "d" }}
df = pd.DataFrame(data)
table = pa.Table.from_pandas(df, pa.schema(fields))
pq.write_table(table, "test.parquet")
{code}
and I am getting:
{noformat}
Traceback (most recent call last):
File "pa_test.py", line 17, in <module>
table = pa.Table.from_pandas(df, pa.schema(fields))
File "pyarrow/table.pxi", line 1451, in pyarrow.lib.Table.from_pandas
File
"/home/tremes/GITHUB/data-pipeline/venv/lib64/python3.7/site-packages/pyarrow/pandas_compat.py",
line 575, in dataframe_to_arrays
for c, f in zip(columns_to_convert, convert_fields)]
File
"/home/tremes/GITHUB/data-pipeline/venv/lib64/python3.7/site-packages/pyarrow/pandas_compat.py",
line 575, in <listcomp>
for c, f in zip(columns_to_convert, convert_fields)]
File
"/home/tremes/GITHUB/data-pipeline/venv/lib64/python3.7/site-packages/pyarrow/pandas_compat.py",
line 566, in convert_column
raise e
File
"/home/tremes/GITHUB/data-pipeline/venv/lib64/python3.7/site-packages/pyarrow/pandas_compat.py",
line 560, in convert_column
result = pa.array(col, type=type_, from_pandas=True, safe=safe)
File "pyarrow/array.pxi", line 265, in pyarrow.lib.array
File "pyarrow/array.pxi", line 80, in pyarrow.lib._ndarray_to_array
File "pyarrow/error.pxi", line 106, in pyarrow.lib.check_status
pyarrow.lib.ArrowNotImplementedError: ('Sequence converter for type
dictionary<values=string, indices=int64, ordered=0> not implemented',
'Conversion failed for column object with type object')
{noformat}
Workaround is to use {{df.to_parquet("test.parquet")}}
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