gh:552 - Corrected Series.mean return type (#622)

* corrected Series.mean() to return np.float64

* req changes

* added args to IndexIterScalar

* Update resample.pyi

pandas-stubs/_typing.pyi

@@ -286,6 +286,8 @@ IndexIterScalar: TypeAlias = (
     | float
     | Timestamp
     | Timedelta
+    | np.integer
+    | np.float_
 )
 Scalar: TypeAlias = IndexIterScalar | complex
 ScalarT = TypeVar("ScalarT", bound=Scalar)

pandas-stubs/core/series.pyi

@@ -1609,7 +1609,7 @@ class Series(IndexOpsMixin, NDFrame, Generic[S1]):
         level: None = ...,
         numeric_only: _bool = ...,
         **kwargs,
-    ) -> float: ...
+    ) -> np.float64: ...
     def median(
         self,
         axis: AxisIndex | None = ...,

tests/test_frame.py

@@ -2019,12 +2019,12 @@ def test_groupby_apply() -> None:
     # GH 167
     df = pd.DataFrame({"col1": [1, 2, 3], "col2": [4, 5, 6]})
 
-    def sum_mean(x: pd.DataFrame) -> float:
+    def sum_mean(x: pd.DataFrame) -> np.float64:
         return x.sum().mean()
 
     check(assert_type(df.groupby("col1").apply(sum_mean), pd.Series), pd.Series)
 
-    lfunc: Callable[[pd.DataFrame], float] = lambda x: x.sum().mean()
+    lfunc: Callable[[pd.DataFrame], np.float64] = lambda x: x.sum().mean()
     check(
         assert_type(df.groupby("col1").apply(lfunc), pd.Series),
         pd.Series,

tests/test_resampler.py

@@ -155,7 +155,7 @@ def g(val: DataFrame) -> Series:
 
     check(assert_type(DF.resample("m").pipe(g), DataFrame), DataFrame)
 
-    def h(val: DataFrame) -> float:
+    def h(val: DataFrame) -> np.float64:
         return val.mean().mean()
 
     check(assert_type(DF.resample("m").pipe(h), Series), Series)
@@ -245,10 +245,10 @@ def test_aggregate_series() -> None:
         DataFrame,
     )
 
-    def f(val: Series) -> float:
+    def f(val: Series) -> np.float64:
         return val.mean()
 
-    check(assert_type(S.resample("m").aggregate(f), _AggRetType), Series)
+    check(assert_type(S.resample("m").aggregate(f), _AggRetType), pd.Series)
 
 
 def test_asfreq_series() -> None:

tests/test_series.py

@@ -306,10 +306,10 @@ def test_types_rank() -> None:
 
 def test_types_mean() -> None:
     s = pd.Series([1, 2, 3, np.nan])
-    f1: float = s.mean()
+    check(assert_type(s.mean(), np.float64), np.float64)
     s1: pd.Series = s.groupby(level=0).mean()
-    f2: float = s.mean(skipna=False)
-    f3: float = s.mean(numeric_only=False)
+    f2: np.float64 = s.mean(skipna=False)
+    f3: np.float64 = s.mean(numeric_only=False)
 
 
 def test_types_median() -> None:

tests/test_windowing.py

@@ -148,7 +148,7 @@ def test_rolling_basic_math_series() -> None:
 def test_rolling_apply_series() -> None:
     check(assert_type(S.rolling(10).apply(np.mean), Series), Series)
 
-    def _mean(df: Series) -> float:
+    def _mean(df: Series) -> np.float64:
         return df.mean()
 
     check(assert_type(S.rolling(10).apply(_mean), Series), Series)
@@ -163,7 +163,7 @@ def test_rolling_aggregate_series() -> None:
     check(assert_type(S.rolling(10).aggregate(np.mean), Series), Series)
     check(assert_type(S.rolling(10).aggregate("mean"), Series), Series)
 
-    def _mean(s: Series) -> float:
+    def _mean(s: Series) -> np.float64:
         return s.mean()
 
     check(assert_type(S.rolling(10).aggregate(_mean), Series), Series)
@@ -256,7 +256,7 @@ def test_expanding_basic_math_series() -> None:
 def test_expanding_apply_series() -> None:
     check(assert_type(S.expanding(10).apply(np.mean), Series), Series)
 
-    def _mean(df: Series) -> float:
+    def _mean(df: Series) -> np.float64:
         return df.mean()
 
     check(assert_type(S.expanding(10).apply(_mean), Series), Series)