TYP: Specify how in dropna (pandas-dev#48289)

Author: phofl

pandas/core/frame.py

@@ -6423,7 +6423,7 @@ def dropna(
         self,
         *,
         axis: Axis = ...,
-        how: str | NoDefault = ...,
+        how: Literal["any", "all"] | NoDefault = ...,
         thresh: int | NoDefault = ...,
         subset: IndexLabel = ...,
         inplace: Literal[False] = ...,
@@ -6435,7 +6435,7 @@ def dropna(
         self,
         *,
         axis: Axis = ...,
-        how: str | NoDefault = ...,
+        how: Literal["any", "all"] | NoDefault = ...,
         thresh: int | NoDefault = ...,
         subset: IndexLabel = ...,
         inplace: Literal[True],
@@ -6446,7 +6446,7 @@ def dropna(
     def dropna(
         self,
         axis: Axis = 0,
-        how: str | NoDefault = no_default,
+        how: Literal["any", "all"] | NoDefault = no_default,
         thresh: int | NoDefault = no_default,
         subset: IndexLabel = None,
         inplace: bool = False,

pandas/core/indexes/base.py

@@ -2971,7 +2971,7 @@ def fillna(self, value=None, downcast=None):
             )
         return self._view()
 
-    def dropna(self: _IndexT, how: str_t = "any") -> _IndexT:
+    def dropna(self: _IndexT, how: Literal["any", "all"] = "any") -> _IndexT:
         """
         Return Index without NA/NaN values.
 

pandas/core/indexes/multi.py

@@ -1634,7 +1634,7 @@ def fillna(self, value=None, downcast=None):
         raise NotImplementedError("isna is not defined for MultiIndex")
 
     @doc(Index.dropna)
-    def dropna(self, how: str = "any") -> MultiIndex:
+    def dropna(self, how: Literal["any", "all"] = "any") -> MultiIndex:
         nans = [level_codes == -1 for level_codes in self.codes]
         if how == "any":
             indexer = np.any(nans, axis=0)

pandas/core/series.py

@@ -5731,19 +5731,30 @@ def notnull(self) -> Series:
 
     @overload
     def dropna(
-        self, *, axis: Axis = ..., inplace: Literal[False] = ..., how: str | None = ...
+        self,
+        *,
+        axis: Axis = ...,
+        inplace: Literal[False] = ...,
+        how: Literal["any", "all"] | None = ...,
     ) -> Series:
         ...
 
     @overload
     def dropna(
-        self, *, axis: Axis = ..., inplace: Literal[True], how: str | None = ...
+        self,
+        *,
+        axis: Axis = ...,
+        inplace: Literal[True],
+        how: Literal["any", "all"] | None = ...,
     ) -> None:
         ...
 
     @deprecate_nonkeyword_arguments(version=None, allowed_args=["self"])
     def dropna(
-        self, axis: Axis = 0, inplace: bool = False, how: str | None = None
+        self,
+        axis: Axis = 0,
+        inplace: bool = False,
+        how: Literal["any", "all"] | None = None,
     ) -> Series | None:
         """
         Return a new Series with missing values removed.