ENH: Add errors='coerce' to DataFrame.astype / Series.astype (GH#48781)

[berasaikat]

Closes #48781

---

Add errors='coerce' as a option. Unconvertible values are replaced with the dtype's NA sentinel instead of raising:

df = pd.DataFrame({"a": [1, 2, "ERR"], "b": [3.0, "bad", 5.0]})

df.astype(float, errors="coerce")
#      a    b
# 0  1.0  3.0
# 1  2.0  NaN
# 2  NaN  5.0

df.astype("Float64", errors="coerce")
#       a     b
# 0   1.0   3.0
# 1   2.0  <NA>
# 2  <NA>   5.0

df.astype({"a": "Int64", "b": "datetime64[us]"}, errors="coerce")
# per-column dict form also supported

Files changed

• pandas/_typing.py — add IgnoreRaiseCoerce
• pandas/core/dtypes/astype.py — astype_array_safe coerce branch + _coerce_to_na helper
• pandas/core/generic.py — widen errors type + docstring + examples
• pandas/core/internals/blocks.py — widen errors type
• pandas/tests/frame/methods/test_astype.py — TestAstypeCoerce
• pandas/tests/series/methods/test_astype.py — TestSeriesAstypeCoerce
• doc/source/whatsnew/v3.1.0.rst — enhancement entry

---

Checklist

• Tests added in TestAstypeCoerce (DataFrame) and TestSeriesAstypeCoerce (Series) covering: float coerce, nullable Float64/Int64, datetime, dict-dtype, all-valid parity with errors='raise', and invalid errors= kwarg
• Whatsnew entry added
• Docstring updated with new errors option description and examples

[Dr-Irv]

I only reviewed pandas/_typing.py

[Dr-Irv]

Suggested change

	IgnoreRaiseCoerce: TypeAlias = Literal["ignore", "raise", "coerce"]
	IgnoreRaiseCoerce: TypeAlias = IgnoreRaise | Literal["coerce"]

[Dr-Irv]

I approve the changes to pandas/_typing.py. Others will need to approve the rest of this.

[jbrockmendel]

Possible xref #45588. Can you see if this helps accomplish that?