REF: catch less in maybe_cast_to_datetime (#40037)

Author: jbrockmendel

pandas/_libs/tslibs/timedeltas.pyx

@@ -347,9 +347,13 @@ def array_to_timedelta64(ndarray[object] values, str unit=None, str errors="rais
         for i in range(n):
             try:
                 result[i] = convert_to_timedelta64(values[i], parsed_unit)
-            except ValueError:
+            except ValueError as err:
                 if errors == 'coerce':
                     result[i] = NPY_NAT
+                elif "unit abbreviation w/o a number" in str(err):
+                    # re-raise with more pertinent message
+                    msg = f"Could not convert '{values[i]}' to NumPy timedelta"
+                    raise ValueError(msg) from err
                 else:
                     raise
 

pandas/core/dtypes/cast.py

@@ -26,6 +26,7 @@
 )
 import warnings
 
+from dateutil.parser import ParserError
 import numpy as np
 
 from pandas._libs import (
@@ -1315,11 +1316,7 @@ def convert_dtypes(
     if (
         convert_string or convert_integer or convert_boolean or convert_floating
     ) and not is_extension:
-        try:
-            inferred_dtype = lib.infer_dtype(input_array)
-        except ValueError:
-            # Required to catch due to Period.  Can remove once GH 23553 is fixed
-            inferred_dtype = input_array.dtype
+        inferred_dtype = lib.infer_dtype(input_array)
 
         if not convert_string and is_string_dtype(inferred_dtype):
             inferred_dtype = input_array.dtype
@@ -1591,8 +1588,19 @@ def maybe_cast_to_datetime(
                             value = to_timedelta(value, errors="raise")._values
                     except OutOfBoundsDatetime:
                         raise
-                    except (ValueError, TypeError):
+                    except ParserError:
+                        # Note: ParserError subclasses ValueError
+                        # str that we can't parse to datetime
                         pass
+                    except ValueError as err:
+                        if "mixed datetimes and integers in passed array" in str(err):
+                            # array_to_datetime does not allow this;
+                            # when called from _try_cast, this will be followed
+                            #  by a call to construct_1d_ndarray_preserving_na
+                            #  which will convert these
+                            pass
+                        else:
+                            raise
 
         # coerce datetimelike to object
         elif is_datetime64_dtype(

pandas/tests/frame/test_constructors.py

@@ -85,6 +85,8 @@ def test_array_of_dt64_nat_with_td64dtype_raises(self, frame_or_series):
             arr = arr.reshape(1, 1)
 
         msg = "Could not convert object to NumPy timedelta"
+        if frame_or_series is Series:
+            msg = "Invalid type for timedelta scalar: <class 'numpy.datetime64'>"
         with pytest.raises(ValueError, match=msg):
             frame_or_series(arr, dtype="m8[ns]")
 

pandas/tests/indexes/datetimes/test_indexing.py

@@ -617,7 +617,8 @@ def test_get_indexer(self):
             pd.Timedelta("1 hour").to_timedelta64(),
             "foo",
         ]
-        with pytest.raises(ValueError, match="abbreviation w/o a number"):
+        msg = "Could not convert 'foo' to NumPy timedelta"
+        with pytest.raises(ValueError, match=msg):
             idx.get_indexer(target, "nearest", tolerance=tol_bad)
         with pytest.raises(ValueError, match="abbreviation w/o a number"):
             idx.get_indexer(idx[[0]], method="nearest", tolerance="foo")

pandas/tests/series/test_constructors.py

@@ -1332,7 +1332,7 @@ def test_constructor_dtype_timedelta64(self):
             td.astype("int32")
 
         # this is an invalid casting
-        msg = "Could not convert object to NumPy timedelta"
+        msg = "Could not convert 'foo' to NumPy timedelta"
         with pytest.raises(ValueError, match=msg):
             Series([timedelta(days=1), "foo"], dtype="m8[ns]")
 

pandas/tests/tools/test_to_timedelta.py

@@ -124,9 +124,10 @@ def test_to_timedelta_invalid(self):
             to_timedelta(time(second=1))
         assert to_timedelta(time(second=1), errors="coerce") is pd.NaT
 
-        msg = "unit abbreviation w/o a number"
+        msg = "Could not convert 'foo' to NumPy timedelta"
         with pytest.raises(ValueError, match=msg):
             to_timedelta(["foo", "bar"])
+
         tm.assert_index_equal(
             TimedeltaIndex([pd.NaT, pd.NaT]),
             to_timedelta(["foo", "bar"], errors="coerce"),