staticmethods to _pyarrow_write_attrs/_pyarrow_read_attrs|add docstri…

…ng/types

pandas/io/parquet.py

@@ -143,6 +143,44 @@ def read(self, path, columns=None, **kwargs):
         raise AbstractMethodError(self)
 
 
+def _pyarrow_write_attrs(table: Any, df: DataFrame) -> Any:
+    """
+    .. versionadded:: 1.3
+
+    Copy attts from pandas.DataFrame and pandas.Series to
+    schema metadata in pyarrow.Table.
+    """
+    schema_metadata = table.schema.metadata or {}
+    pandas_metadata = json.loads(schema_metadata.get(b"pandas", "{}"))
+    column_attrs = {}
+    for col in df.columns:
+        attrs = df[col].attrs
+        if not attrs or not isinstance(col, str):
+            continue
+        column_attrs[col] = attrs
+    pandas_metadata.update(
+        attrs=df.attrs,
+        column_attrs=column_attrs,
+    )
+    schema_metadata[b"pandas"] = json.dumps(pandas_metadata)
+    return table.replace_schema_metadata(schema_metadata)
+
+
+def _pyarrow_read_attrs(table: Any, df: DataFrame) -> None:
+    """
+    .. versionadded:: 1.3
+
+    Copy schema metadata from pyarrow.Table
+    to attrs in pandas.DataFrame and pandas.Series.
+    """
+    schema_metadata = table.schema.metadata or {}
+    pandas_metadata = json.loads(schema_metadata.get(b"pandas", "{}"))
+    df.attrs = pandas_metadata.get("attrs", {})
+    col_attrs = pandas_metadata.get("column_attrs", {})
+    for col in df.columns:
+        df[col].attrs = col_attrs.get(col, {})
+
+
 class PyArrowImpl(BaseImpl):
     def __init__(self):
         import_optional_dependency(
@@ -155,32 +193,6 @@ def __init__(self):
 
         self.api = pyarrow
 
-    @staticmethod
-    def _write_attrs(table, df: DataFrame):
-        schema_metadata = table.schema.metadata or {}
-        pandas_metadata = json.loads(schema_metadata.get(b"pandas", "{}"))
-        column_attrs = {}
-        for col in df.columns:
-            attrs = df[col].attrs
-            if not attrs or not isinstance(col, str):
-                continue
-            column_attrs[col] = attrs
-        pandas_metadata.update(
-            attrs=df.attrs,
-            column_attrs=column_attrs,
-        )
-        schema_metadata[b"pandas"] = json.dumps(pandas_metadata)
-        return table.replace_schema_metadata(schema_metadata)
-
-    @staticmethod
-    def _read_attrs(table, df: DataFrame):
-        schema_metadata = table.schema.metadata or {}
-        pandas_metadata = json.loads(schema_metadata.get(b"pandas", "{}"))
-        df.attrs = pandas_metadata.get("attrs", {})
-        col_attrs = pandas_metadata.get("column_attrs", {})
-        for col in df.columns:
-            df[col].attrs = col_attrs.get(col, {})
-
     def write(
         self,
         df: DataFrame,
@@ -198,7 +210,7 @@ def write(
             from_pandas_kwargs["preserve_index"] = index
 
         table = self.api.Table.from_pandas(df, **from_pandas_kwargs)
-        table = self._write_attrs(table, df)
+        table = _pyarrow_write_attrs(table, df)
 
         path_or_handle, handles, kwargs["filesystem"] = _get_path_or_handle(
             path,
@@ -268,7 +280,7 @@ def read(
                 path_or_handle, columns=columns, **kwargs
             )
             result = table.to_pandas(**to_pandas_kwargs)
-            self._read_attrs(table, result)
+            _pyarrow_read_attrs(table, result)
             if manager == "array":
                 result = result._as_manager("array", copy=False)
             return result