refactor: improve from_dataframe method for clarity and add internal DataFrame test

Author: kosiew

python/datafusion/table_provider.py

@@ -56,8 +56,12 @@ def from_dataframe(cls, df: Any) -> TableProvider:
         """Create a :class:`TableProvider` from a :class:`DataFrame`."""
         from datafusion.dataframe import DataFrame as DataFrameWrapper
 
-        df = df if isinstance(df, DataFrameWrapper) else DataFrameWrapper(df)
-        return df.into_view()
+        if isinstance(df, DataFrameWrapper):
+            dataframe = df
+        else:
+            dataframe = DataFrameWrapper(df)
+
+        return dataframe.into_view()
 
     @classmethod
     def from_view(cls, df: Any) -> TableProvider:

python/tests/test_context.py

@@ -355,11 +355,21 @@ def test_table_provider_from_capsule(ctx):
 def test_table_provider_from_dataframe(ctx):
     df = ctx.from_pydict({"a": [1, 2]})
     provider = TableProvider.from_dataframe(df)
+    assert isinstance(provider, TableProvider)
     ctx.register_table("from_dataframe_tbl", provider)
     result = ctx.sql("SELECT * FROM from_dataframe_tbl").collect()
     assert [b.to_pydict() for b in result] == [{"a": [1, 2]}]
 
 
+def test_table_provider_from_dataframe_internal(ctx):
+    df = ctx.from_pydict({"a": [1, 2]})
+    provider = TableProvider.from_dataframe(df.df)
+    assert isinstance(provider, TableProvider)
+    ctx.register_table("from_internal_dataframe_tbl", provider)
+    result = ctx.sql("SELECT * FROM from_internal_dataframe_tbl").collect()
+    assert [b.to_pydict() for b in result] == [{"a": [1, 2]}]
+
+
 def test_table_provider_from_view_warning_origin(ctx):
     from datafusion.table_provider import TableProvider as WrapperTableProvider