TYP: make dtype required in _from_sequence_of_strings (#56519)

* TYP: make dtype required in _from_sequence_of_strings

* GH ref

* mypy fixup

* Move whatsnew

* Update pandas/core/arrays/base.py

Co-authored-by: Matthew Roeschke <[email protected]>

---------

Co-authored-by: Matthew Roeschke <[email protected]>

Author: jbrockmendel

doc/source/whatsnew/v3.0.0.rst

@@ -88,6 +88,7 @@ Other API changes
 ^^^^^^^^^^^^^^^^^
 - 3rd party ``py.path`` objects are no longer explicitly supported in IO methods. Use :py:class:`pathlib.Path` objects instead (:issue:`57091`)
 - :attr:`MultiIndex.codes`, :attr:`MultiIndex.levels`, and :attr:`MultiIndex.names` now returns a ``tuple`` instead of a ``FrozenList`` (:issue:`53531`)
+- Made ``dtype`` a required argument in :meth:`ExtensionArray._from_sequence_of_strings` (:issue:`56519`)
 - pickle and HDF (``.h5``) files created with Python 2 are no longer explicitly supported (:issue:`57387`)
 -
 

pandas/core/arrays/arrow/array.py

@@ -199,6 +199,8 @@ def floordiv_compat(
         npt,
     )
 
+    from pandas.core.dtypes.dtypes import ExtensionDtype
+
     from pandas import Series
     from pandas.core.arrays.datetimes import DatetimeArray
     from pandas.core.arrays.timedeltas import TimedeltaArray
@@ -316,7 +318,7 @@ def _from_sequence(
 
     @classmethod
     def _from_sequence_of_strings(
-        cls, strings, *, dtype: Dtype | None = None, copy: bool = False
+        cls, strings, *, dtype: ExtensionDtype, copy: bool = False
     ) -> Self:
         """
         Construct a new ExtensionArray from a sequence of strings.
@@ -533,8 +535,9 @@ def _box_pa_array(
                     ):
                         # TODO: Move logic in _from_sequence_of_strings into
                         # _box_pa_array
+                        dtype = ArrowDtype(pa_type)
                         return cls._from_sequence_of_strings(
-                            value, dtype=pa_type
+                            value, dtype=dtype
                         )._pa_array
                     else:
                         raise

pandas/core/arrays/base.py

@@ -332,7 +332,7 @@ def _from_scalars(cls, scalars, *, dtype: DtypeObj) -> Self:
 
     @classmethod
     def _from_sequence_of_strings(
-        cls, strings, *, dtype: Dtype | None = None, copy: bool = False
+        cls, strings, *, dtype: ExtensionDtype, copy: bool = False
     ) -> Self:
         """
         Construct a new ExtensionArray from a sequence of strings.
@@ -342,7 +342,7 @@ def _from_sequence_of_strings(
         strings : Sequence
             Each element will be an instance of the scalar type for this
             array, ``cls.dtype.type``.
-        dtype : dtype, optional
+        dtype : ExtensionDtype
             Construct for this particular dtype. This should be a Dtype
             compatible with the ExtensionArray.
         copy : bool, default False
@@ -354,7 +354,9 @@ def _from_sequence_of_strings(
 
         Examples
         --------
-        >>> pd.arrays.IntegerArray._from_sequence_of_strings(["1", "2", "3"])
+        >>> pd.arrays.IntegerArray._from_sequence_of_strings(
+        ...     ["1", "2", "3"], dtype=pd.Int64Dtype()
+        ... )
         <IntegerArray>
         [1, 2, 3]
         Length: 3, dtype: Int64

pandas/core/arrays/boolean.py

@@ -29,13 +29,14 @@
     import pyarrow
 
     from pandas._typing import (
-        Dtype,
         DtypeObj,
         Self,
         npt,
         type_t,
     )
 
+    from pandas.core.dtypes.dtypes import ExtensionDtype
+
 
 @register_extension_dtype
 class BooleanDtype(BaseMaskedDtype):
@@ -324,7 +325,7 @@ def _from_sequence_of_strings(
         cls,
         strings: list[str],
         *,
-        dtype: Dtype | None = None,
+        dtype: ExtensionDtype,
         copy: bool = False,
         true_values: list[str] | None = None,
         false_values: list[str] | None = None,

pandas/core/arrays/numeric.py

@@ -33,12 +33,13 @@
     import pyarrow
 
     from pandas._typing import (
-        Dtype,
         DtypeObj,
         Self,
         npt,
     )
 
+    from pandas.core.dtypes.dtypes import ExtensionDtype
+
 
 class NumericDtype(BaseMaskedDtype):
     _default_np_dtype: np.dtype
@@ -270,7 +271,7 @@ def _coerce_to_array(
 
     @classmethod
     def _from_sequence_of_strings(
-        cls, strings, *, dtype: Dtype | None = None, copy: bool = False
+        cls, strings, *, dtype: ExtensionDtype, copy: bool = False
     ) -> Self:
         from pandas.core.tools.numeric import to_numeric
 

pandas/core/arrays/period.py

@@ -90,6 +90,8 @@
         npt,
     )
 
+    from pandas.core.dtypes.dtypes import ExtensionDtype
+
     from pandas.core.arrays import (
         DatetimeArray,
         TimedeltaArray,
@@ -303,7 +305,7 @@ def _from_sequence(
 
     @classmethod
     def _from_sequence_of_strings(
-        cls, strings, *, dtype: Dtype | None = None, copy: bool = False
+        cls, strings, *, dtype: ExtensionDtype, copy: bool = False
     ) -> Self:
         return cls._from_sequence(strings, dtype=dtype, copy=copy)
 

pandas/core/arrays/string_.py

@@ -416,7 +416,7 @@ def _from_sequence(
 
     @classmethod
     def _from_sequence_of_strings(
-        cls, strings, *, dtype: Dtype | None = None, copy: bool = False
+        cls, strings, *, dtype: ExtensionDtype, copy: bool = False
     ) -> Self:
         return cls._from_sequence(strings, dtype=dtype, copy=copy)
 

pandas/core/arrays/string_arrow.py

@@ -62,6 +62,8 @@
         npt,
     )
 
+    from pandas.core.dtypes.dtypes import ExtensionDtype
+
     from pandas import Series
 
 
@@ -202,7 +204,7 @@ def _from_sequence(
 
     @classmethod
     def _from_sequence_of_strings(
-        cls, strings, dtype: Dtype | None = None, copy: bool = False
+        cls, strings, *, dtype: ExtensionDtype, copy: bool = False
     ) -> Self:
         return cls._from_sequence(strings, dtype=dtype, copy=copy)
 

pandas/tests/arrays/boolean/test_construction.py

@@ -243,7 +243,7 @@ def test_coerce_to_numpy_array():
 def test_to_boolean_array_from_strings():
     result = BooleanArray._from_sequence_of_strings(
         np.array(["True", "False", "1", "1.0", "0", "0.0", np.nan], dtype=object),
-        dtype="boolean",
+        dtype=pd.BooleanDtype(),
     )
     expected = BooleanArray(
         np.array([True, False, True, True, False, False, False]),
@@ -255,7 +255,7 @@ def test_to_boolean_array_from_strings():
 
 def test_to_boolean_array_from_strings_invalid_string():
     with pytest.raises(ValueError, match="cannot be cast"):
-        BooleanArray._from_sequence_of_strings(["donkey"], dtype="boolean")
+        BooleanArray._from_sequence_of_strings(["donkey"], dtype=pd.BooleanDtype())
 
 
 @pytest.mark.parametrize("box", [True, False], ids=["series", "array"])

pandas/tests/extension/decimal/array.py

@@ -101,7 +101,7 @@ def _from_sequence(cls, scalars, *, dtype=None, copy=False):
         return cls(scalars)
 
     @classmethod
-    def _from_sequence_of_strings(cls, strings, dtype=None, copy=False):
+    def _from_sequence_of_strings(cls, strings, *, dtype: ExtensionDtype, copy=False):
         return cls._from_sequence(
             [decimal.Decimal(x) for x in strings], dtype=dtype, copy=copy
         )

pandas/tests/extension/test_arrow.py

@@ -354,10 +354,9 @@ def test_from_sequence_pa_array(self, data):
         assert isinstance(result._pa_array, pa.ChunkedArray)
 
     def test_from_sequence_pa_array_notimplemented(self, request):
+        dtype = ArrowDtype(pa.month_day_nano_interval())
         with pytest.raises(NotImplementedError, match="Converting strings to"):
-            ArrowExtensionArray._from_sequence_of_strings(
-                ["12-1"], dtype=pa.month_day_nano_interval()
-            )
+            ArrowExtensionArray._from_sequence_of_strings(["12-1"], dtype=dtype)
 
     def test_from_sequence_of_strings_pa_array(self, data, request):
         pa_dtype = data.dtype.pyarrow_dtype
@@ -2409,7 +2408,8 @@ def test_duration_from_strings_with_nat(unit):
     # GH51175
     strings = ["1000", "NaT"]
     pa_type = pa.duration(unit)
-    result = ArrowExtensionArray._from_sequence_of_strings(strings, dtype=pa_type)
+    dtype = ArrowDtype(pa_type)
+    result = ArrowExtensionArray._from_sequence_of_strings(strings, dtype=dtype)
     expected = ArrowExtensionArray(pa.array([1000, None], type=pa_type))
     tm.assert_extension_array_equal(result, expected)
 
@@ -2928,13 +2928,14 @@ def test_from_sequence_of_strings_boolean():
         [True] * len(true_strings) + [False] * len(false_strings) + [None] * len(nulls)
     )
 
-    result = ArrowExtensionArray._from_sequence_of_strings(strings, dtype=pa.bool_())
+    dtype = ArrowDtype(pa.bool_())
+    result = ArrowExtensionArray._from_sequence_of_strings(strings, dtype=dtype)
     expected = pd.array(bools, dtype="boolean[pyarrow]")
     tm.assert_extension_array_equal(result, expected)
 
     strings = ["True", "foo"]
     with pytest.raises(pa.ArrowInvalid, match="Failed to parse"):
-        ArrowExtensionArray._from_sequence_of_strings(strings, dtype=pa.bool_())
+        ArrowExtensionArray._from_sequence_of_strings(strings, dtype=dtype)
 
 
 def test_concat_empty_arrow_backed_series(dtype):