TYP: core/dtypes/cast.py (pandas-dev#37024)

Author: arw2019

pandas/core/dtypes/cast.py

@@ -4,7 +4,18 @@
 
 from contextlib import suppress
 from datetime import date, datetime, timedelta
-from typing import TYPE_CHECKING, Any, List, Optional, Tuple, Type
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    List,
+    Optional,
+    Sequence,
+    Set,
+    Sized,
+    Tuple,
+    Type,
+    Union,
+)
 
 import numpy as np
 
@@ -21,7 +32,7 @@
     ints_to_pytimedelta,
 )
 from pandas._libs.tslibs.timezones import tz_compare
-from pandas._typing import ArrayLike, Dtype, DtypeObj
+from pandas._typing import AnyArrayLike, ArrayLike, Dtype, DtypeObj, Scalar
 from pandas.util._validators import validate_bool_kwarg
 
 from pandas.core.dtypes.common import (
@@ -86,6 +97,8 @@
 if TYPE_CHECKING:
     from pandas import Series
     from pandas.core.arrays import ExtensionArray
+    from pandas.core.indexes.base import Index
+    from pandas.core.indexes.datetimes import DatetimeIndex
 
 _int8_max = np.iinfo(np.int8).max
 _int16_max = np.iinfo(np.int16).max
@@ -121,7 +134,7 @@ def is_nested_object(obj) -> bool:
     return False
 
 
-def maybe_downcast_to_dtype(result, dtype):
+def maybe_downcast_to_dtype(result, dtype: Dtype):
     """
     try to cast to the specified dtype (e.g. convert back to bool/int
     or could be an astype of float64->float32
@@ -186,7 +199,7 @@ def maybe_downcast_to_dtype(result, dtype):
     return result
 
 
-def maybe_downcast_numeric(result, dtype, do_round: bool = False):
+def maybe_downcast_numeric(result, dtype: DtypeObj, do_round: bool = False):
     """
     Subset of maybe_downcast_to_dtype restricted to numeric dtypes.
 
@@ -329,7 +342,9 @@ def maybe_cast_result_dtype(dtype: DtypeObj, how: str) -> DtypeObj:
     return dtype
 
 
-def maybe_cast_to_extension_array(cls: Type["ExtensionArray"], obj, dtype=None):
+def maybe_cast_to_extension_array(
+    cls: Type["ExtensionArray"], obj: ArrayLike, dtype: Optional[ExtensionDtype] = None
+) -> ArrayLike:
     """
     Call to `_from_sequence` that returns the object unchanged on Exception.
 
@@ -362,7 +377,9 @@ def maybe_cast_to_extension_array(cls: Type["ExtensionArray"], obj, dtype=None):
     return result
 
 
-def maybe_upcast_putmask(result: np.ndarray, mask: np.ndarray, other):
+def maybe_upcast_putmask(
+    result: np.ndarray, mask: np.ndarray, other: Scalar
+) -> Tuple[np.ndarray, bool]:
     """
     A safe version of putmask that potentially upcasts the result.
 
@@ -444,7 +461,9 @@ def changeit():
     return result, False
 
 
-def maybe_casted_values(index, codes=None):
+def maybe_casted_values(
+    index: "Index", codes: Optional[np.ndarray] = None
+) -> ArrayLike:
     """
     Convert an index, given directly or as a pair (level, code), to a 1D array.
 
@@ -468,7 +487,7 @@ def maybe_casted_values(index, codes=None):
 
     # if we have the codes, extract the values with a mask
     if codes is not None:
-        mask = codes == -1
+        mask: np.ndarray = codes == -1
 
         # we can have situations where the whole mask is -1,
         # meaning there is nothing found in codes, so make all nan's
@@ -660,7 +679,7 @@ def maybe_promote(dtype, fill_value=np.nan):
     return dtype, fill_value
 
 
-def _ensure_dtype_type(value, dtype):
+def _ensure_dtype_type(value, dtype: DtypeObj):
     """
     Ensure that the given value is an instance of the given dtype.
 
@@ -786,8 +805,9 @@ def infer_dtype_from_scalar(val, pandas_dtype: bool = False) -> Tuple[DtypeObj,
     return dtype, val
 
 
-# TODO: try to make the Any in the return annotation more specific
-def infer_dtype_from_array(arr, pandas_dtype: bool = False) -> Tuple[DtypeObj, Any]:
+def infer_dtype_from_array(
+    arr, pandas_dtype: bool = False
+) -> Tuple[DtypeObj, ArrayLike]:
     """
     Infer the dtype from an array.
 
@@ -875,7 +895,12 @@ def maybe_infer_dtype_type(element):
     return tipo
 
 
-def maybe_upcast(values, fill_value=np.nan, dtype=None, copy: bool = False):
+def maybe_upcast(
+    values: ArrayLike,
+    fill_value: Scalar = np.nan,
+    dtype: Dtype = None,
+    copy: bool = False,
+) -> Tuple[ArrayLike, Scalar]:
     """
     Provide explicit type promotion and coercion.
 
@@ -887,6 +912,13 @@ def maybe_upcast(values, fill_value=np.nan, dtype=None, copy: bool = False):
     dtype : if None, then use the dtype of the values, else coerce to this type
     copy : bool, default True
         If True always make a copy even if no upcast is required.
+
+    Returns
+    -------
+    values: ndarray or ExtensionArray
+        the original array, possibly upcast
+    fill_value:
+        the fill value, possibly upcast
     """
     if not is_scalar(fill_value) and not is_object_dtype(values.dtype):
         # We allow arbitrary fill values for object dtype
@@ -907,7 +939,7 @@ def maybe_upcast(values, fill_value=np.nan, dtype=None, copy: bool = False):
     return values, fill_value
 
 
-def invalidate_string_dtypes(dtype_set):
+def invalidate_string_dtypes(dtype_set: Set[DtypeObj]):
     """
     Change string like dtypes to object for
     ``DataFrame.select_dtypes()``.
@@ -929,7 +961,7 @@ def coerce_indexer_dtype(indexer, categories):
     return ensure_int64(indexer)
 
 
-def coerce_to_dtypes(result, dtypes):
+def coerce_to_dtypes(result: Sequence[Scalar], dtypes: Sequence[Dtype]) -> List[Scalar]:
     """
     given a dtypes and a result set, coerce the result elements to the
     dtypes
@@ -959,7 +991,9 @@ def conv(r, dtype):
     return [conv(r, dtype) for r, dtype in zip(result, dtypes)]
 
 
-def astype_nansafe(arr, dtype, copy: bool = True, skipna: bool = False):
+def astype_nansafe(
+    arr, dtype: DtypeObj, copy: bool = True, skipna: bool = False
+) -> ArrayLike:
     """
     Cast the elements of an array to a given dtype a nan-safe manner.
 
@@ -1063,7 +1097,9 @@ def astype_nansafe(arr, dtype, copy: bool = True, skipna: bool = False):
     return arr.view(dtype)
 
 
-def maybe_convert_objects(values: np.ndarray, convert_numeric: bool = True):
+def maybe_convert_objects(
+    values: np.ndarray, convert_numeric: bool = True
+) -> Union[np.ndarray, "DatetimeIndex"]:
     """
     If we have an object dtype array, try to coerce dates and/or numbers.
 
@@ -1184,7 +1220,7 @@ def soft_convert_objects(
 
 
 def convert_dtypes(
-    input_array,
+    input_array: AnyArrayLike,
     convert_string: bool = True,
     convert_integer: bool = True,
     convert_boolean: bool = True,
@@ -1195,7 +1231,7 @@ def convert_dtypes(
 
     Parameters
     ----------
-    input_array : ExtensionArray or PandasArray
+    input_array : ExtensionArray, Index, Series or np.ndarray
     convert_string : bool, default True
         Whether object dtypes should be converted to ``StringDtype()``.
     convert_integer : bool, default True
@@ -1250,9 +1286,11 @@ def convert_dtypes(
     return inferred_dtype
 
 
-def maybe_castable(arr) -> bool:
+def maybe_castable(arr: np.ndarray) -> bool:
     # return False to force a non-fastpath
 
+    assert isinstance(arr, np.ndarray)  # GH 37024
+
     # check datetime64[ns]/timedelta64[ns] are valid
     # otherwise try to coerce
     kind = arr.dtype.kind
@@ -1264,7 +1302,9 @@ def maybe_castable(arr) -> bool:
     return arr.dtype.name not in POSSIBLY_CAST_DTYPES
 
 
-def maybe_infer_to_datetimelike(value, convert_dates: bool = False):
+def maybe_infer_to_datetimelike(
+    value: Union[ArrayLike, Scalar], convert_dates: bool = False
+):
     """
     we might have a array (or single object) that is datetime like,
     and no dtype is passed don't change the value unless we find a
@@ -1371,7 +1411,7 @@ def try_timedelta(v):
     return value
 
 
-def maybe_cast_to_datetime(value, dtype, errors: str = "raise"):
+def maybe_cast_to_datetime(value, dtype: DtypeObj, errors: str = "raise"):
     """
     try to cast the array/value to a datetimelike dtype, converting float
     nan to iNaT
@@ -1564,7 +1604,9 @@ def find_common_type(types: List[DtypeObj]) -> DtypeObj:
     return np.find_common_type(types, [])
 
 
-def cast_scalar_to_array(shape, value, dtype: Optional[DtypeObj] = None) -> np.ndarray:
+def cast_scalar_to_array(
+    shape: Tuple, value: Scalar, dtype: Optional[DtypeObj] = None
+) -> np.ndarray:
     """
     Create np.ndarray of specified shape and dtype, filled with values.
 
@@ -1592,7 +1634,7 @@ def cast_scalar_to_array(shape, value, dtype: Optional[DtypeObj] = None) -> np.n
 
 
 def construct_1d_arraylike_from_scalar(
-    value, length: int, dtype: DtypeObj
+    value: Scalar, length: int, dtype: DtypeObj
 ) -> ArrayLike:
     """
     create a np.ndarray / pandas type of specified shape and dtype
@@ -1636,7 +1678,7 @@ def construct_1d_arraylike_from_scalar(
     return subarr
 
 
-def construct_1d_object_array_from_listlike(values) -> np.ndarray:
+def construct_1d_object_array_from_listlike(values: Sized) -> np.ndarray:
     """
     Transform any list-like object in a 1-dimensional numpy array of object
     dtype.
@@ -1662,7 +1704,7 @@ def construct_1d_object_array_from_listlike(values) -> np.ndarray:
 
 
 def construct_1d_ndarray_preserving_na(
-    values, dtype: Optional[DtypeObj] = None, copy: bool = False
+    values: Sequence, dtype: Optional[DtypeObj] = None, copy: bool = False
 ) -> np.ndarray:
     """
     Construct a new ndarray, coercing `values` to `dtype`, preserving NA.
@@ -1696,7 +1738,7 @@ def construct_1d_ndarray_preserving_na(
     return subarr
 
 
-def maybe_cast_to_integer_array(arr, dtype, copy: bool = False):
+def maybe_cast_to_integer_array(arr, dtype: Dtype, copy: bool = False):
     """
     Takes any dtype and returns the casted version, raising for when data is
     incompatible with integer/unsigned integer dtypes.
@@ -1768,7 +1810,7 @@ def maybe_cast_to_integer_array(arr, dtype, copy: bool = False):
         raise ValueError("Trying to coerce float values to integers")
 
 
-def convert_scalar_for_putitemlike(scalar, dtype: np.dtype):
+def convert_scalar_for_putitemlike(scalar: Scalar, dtype: np.dtype) -> Scalar:
     """
     Convert datetimelike scalar if we are setting into a datetime64
     or timedelta64 ndarray.
@@ -1799,7 +1841,7 @@ def convert_scalar_for_putitemlike(scalar, dtype: np.dtype):
     return scalar
 
 
-def validate_numeric_casting(dtype: np.dtype, value):
+def validate_numeric_casting(dtype: np.dtype, value: Scalar) -> None:
     """
     Check that we can losslessly insert the given value into an array
     with the given dtype.