Function _get_columns_to_convert

python/pyarrow/pandas_compat.py:387–452

(df, schema, preserve_index, columns)

def _get_columns_to_convert(df, schema, preserve_index, columns):
    columns = _resolve_columns_of_interest(df, schema, columns)

    if not df.columns.is_unique:
        raise ValueError(
            f'Duplicate column names found: {list(df.columns)}'
        )

    if schema is not None:
        return _get_columns_to_convert_given_schema(df, schema, preserve_index)

    column_names = []
    column_field_names = []

    index_levels = (
        _get_index_level_values(df.index) if preserve_index is not False
        else []
    )

    columns_to_convert = []
    convert_fields = []

    for name in columns:
        col = df[name]
        name = _column_name_to_strings(name)

        if _pandas_api.is_sparse(col):
            raise TypeError(
                f"Sparse pandas data (column {name}) not supported.")

        columns_to_convert.append(col)
        convert_fields.append(None)
        column_names.append(name)
        column_field_names.append(str(name))

    index_descriptors = []
    index_column_names = []
    for i, index_level in enumerate(index_levels):
        name = _index_level_name(
            index_level, i, column_names + index_column_names
        )
        if (isinstance(index_level, _pandas_api.pd.RangeIndex) and
                preserve_index is None):
            descr = _get_range_index_descriptor(index_level)
        else:
            columns_to_convert.append(index_level)
            convert_fields.append(None)
            descr = name
            index_column_names.append(name)
        index_descriptors.append(descr)

    all_names = column_field_names + index_column_names

    # all_names : all of the columns in the resulting table including the data
    # columns and serialized index columns
    # column_names : the names of the data columns
    # index_column_names : the names of the serialized index columns
    # index_descriptors : descriptions of each index to be used for