add Column.len

Author: MarcoGorelli

spec/API_specification/dataframe_api/column_object.py

@@ -90,10 +90,6 @@ def name(self) -> str:
         """Return name of column."""
         ...
 
-    def __len__(self) -> int:
-        """Return the number of rows."""
-        ...
-
     def __iter__(self) -> NoReturn:
         """Iterate over elements.
 
@@ -750,6 +746,10 @@ def var(
         """
         ...
 
+    def len(self) -> Scalar:
+        """Return the number of rows."""
+        ...
+
     def cumulative_max(self) -> Self:
         """Reduction returns a Column.
 

spec/API_specification/dataframe_api/typing.py

@@ -69,7 +69,7 @@ class NullType:
     null: NullType
 
     class Datetime:
-        time_unit: Literal['ms', 'us']
+        time_unit: Literal["ms", "us"]
         time_zone: str | None
 
         def __init__(  # noqa: ANN204
@@ -80,7 +80,7 @@ def __init__(  # noqa: ANN204
             ...
 
     class Duration:
-        time_unit: Literal['ms', 'us']
+        time_unit: Literal["ms", "us"]
 
         def __init__(  # noqa: ANN204
             self,