docs(python): Add warning to count methods on null (#8698)

pola-rs · May 7, 2023 · eac6696 · eac6696
1 parent 726cc99
commit eac6696
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diff --git a/py-polars/polars/dataframe/groupby.py b/py-polars/polars/dataframe/groupby.py
@@ -452,6 +452,9 @@ def count(self) -> DF:
         """
         Count the number of values in each group.
 
+        .. warning::
+            `null` is deemed a value in this context.
+
         Examples
         --------
         >>> df = pl.DataFrame(

diff --git a/py-polars/polars/expr/expr.py b/py-polars/polars/expr/expr.py
@@ -1124,6 +1124,9 @@ def count(self) -> Self:
         """
         Count the number of values in this expression.
 
+        .. warning::
+            `null` is deemed a value in this context.
+
         Examples
         --------
         >>> df = pl.DataFrame({"a": [8, 9, 10], "b": [None, 4, 4]})

diff --git a/py-polars/polars/functions/lazy.py b/py-polars/polars/functions/lazy.py
@@ -291,6 +291,9 @@ def count(column: str | Series | None = None) -> Expr | int:
     """
     Count the number of values in this column/context.
 
+    .. warning::
+        `null` is deemed a value in this context.
+
     Parameters
     ----------
     column

diff --git a/py-polars/polars/lazyframe/groupby.py b/py-polars/polars/lazyframe/groupby.py
@@ -346,6 +346,9 @@ def count(self) -> LDF:
         """
         Count the number of values in each group.
 
+        .. warning::
+            `null` is deemed a value in this context.
+
         Examples
         --------
         >>> ldf = pl.DataFrame(