BUG: Fix for pandas.to_datetime reports incorrect index when failing

doc/source/whatsnew/v3.0.0.rst

@@ -553,6 +553,7 @@ Datetimelike
 - Bug in :meth:`DatetimeIndex.union` and :meth:`DatetimeIndex.intersection` when ``unit`` was non-nanosecond (:issue:`59036`)
 - Bug in :meth:`Series.dt.microsecond` producing incorrect results for pyarrow backed :class:`Series`. (:issue:`59154`)
 - Bug in :meth:`to_datetime` not respecting dayfirst if an uncommon date string was passed. (:issue:`58859`)
+- Bug in :meth:`to_datetime` reports incorrect index in case of any failure scenario. (:issue:`58298`)
 - Bug in setting scalar values with mismatched resolution into arrays with non-nanosecond ``datetime64``, ``timedelta64`` or :class:`DatetimeTZDtype` incorrectly truncating those scalars (:issue:`56410`)
 
 Timedelta

pandas/_libs/tslib.pyx

@@ -439,7 +439,7 @@ cpdef array_to_datetime(
                 raise TypeError(f"{type(val)} is not convertible to datetime")
 
         except (TypeError, OverflowError, ValueError) as ex:
-            ex.args = (f"{ex}, at position {i}",)
+            ex.args = (f"{ex}",)
             if is_coerce:
                 iresult[i] = NPY_NAT
                 continue

pandas/_libs/tslibs/strptime.pyx

@@ -536,7 +536,7 @@ def array_strptime(
 
         except ValueError as ex:
             ex.args = (
-                f"{str(ex)}, at position {i}. You might want to try:\n"
+                f"{str(ex)}. You might want to try:\n"
                 "    - passing `format` if your strings have a consistent format;\n"
                 "    - passing `format='ISO8601'` if your strings are "
                 "all ISO8601 but not necessarily in exactly the same format;\n"

pandas/tests/frame/test_block_internals.py

@@ -251,7 +251,7 @@ def f(dtype):
             f("float64")
 
         # 10822
-        msg = "^Unknown datetime string format, unable to parse: aa, at position 0$"
+        msg = "^Unknown datetime string format, unable to parse: aa$"
         with pytest.raises(ValueError, match=msg):
             f("M8[ns]")
 

pandas/tests/io/parser/test_parse_dates.py

@@ -507,8 +507,8 @@ def test_parse_multiple_delimited_dates_with_swap_warnings():
     with pytest.raises(
         ValueError,
         match=(
-            r'^time data "31/05/2000" doesn\'t match format "%m/%d/%Y", '
-            r"at position 1. You might want to try:"
+            r'^time data "31/05/2000" doesn\'t match format "%m/%d/%Y". '
+            r"You might want to try:"
         ),
     ):
         pd.to_datetime(["01/01/2000", "31/05/2000", "31/05/2001", "01/02/2000"])

pandas/tests/series/test_constructors.py

@@ -83,7 +83,7 @@ def test_infer_with_date_and_datetime(self):
     def test_unparsable_strings_with_dt64_dtype(self):
         # pre-2.0 these would be silently ignored and come back with object dtype
         vals = ["aa"]
-        msg = "^Unknown datetime string format, unable to parse: aa, at position 0$"
+        msg = "^Unknown datetime string format, unable to parse: aa$"
         with pytest.raises(ValueError, match=msg):
             Series(vals, dtype="datetime64[ns]")
 

pandas/tests/tools/test_to_datetime.py

@@ -133,8 +133,7 @@ def test_to_datetime_format_YYYYMMDD_with_nat(self, cache):
         with pytest.raises(
             ValueError,
             match=(
-                'unconverted data remains when parsing with format "%Y%m%d": ".0", '
-                "at position 0"
+                'unconverted data remains when parsing with format "%Y%m%d": ".0". '
             ),
         ):
             # https://github.com/pandas-dev/pandas/issues/50051
@@ -514,10 +513,9 @@ def test_to_datetime_parse_timezone_malformed(self, offset):
 
         msg = "|".join(
             [
-                r'^time data ".*" doesn\'t match format ".*", at position 0. '
+                r'^time data ".*" doesn\'t match format ".*". ' f"{PARSING_ERR_MSG}$",
+                r'^unconverted data remains when parsing with format ".*": ".*". '
                 f"{PARSING_ERR_MSG}$",
-                r'^unconverted data remains when parsing with format ".*": ".*", '
-                f"at position 0. {PARSING_ERR_MSG}$",
             ]
         )
         with pytest.raises(ValueError, match=msg):
@@ -539,7 +537,7 @@ def test_to_datetime_overflow(self):
         # TODO: Timestamp raises ValueError("could not convert string to Timestamp")
         #  can we make these more consistent?
         arg = "08335394550"
-        msg = 'Parsing "08335394550" to datetime overflows, at position 0'
+        msg = 'Parsing "08335394550" to datetime overflows'
         with pytest.raises(OutOfBoundsDatetime, match=msg):
             to_datetime(arg)
 
@@ -1309,8 +1307,8 @@ def test_datetime_bool_arrays_mixed(self, cache):
         with pytest.raises(
             ValueError,
             match=(
-                r'^time data "True" doesn\'t match format "%Y%m%d", '
-                f"at position 1. {PARSING_ERR_MSG}$"
+                r'^time data "True" doesn\'t match format "%Y%m%d". '
+                f"{PARSING_ERR_MSG}$"
             ),
         ):
             to_datetime(["20130101", True], cache=cache)
@@ -1345,12 +1343,12 @@ def test_datetime_invalid_scalar(self, value, format):
 
         msg = "|".join(
             [
-                r'^time data "a" doesn\'t match format "%H:%M:%S", at position 0. '
+                r'^time data "a" doesn\'t match format "%H:%M:%S". '
                 f"{PARSING_ERR_MSG}$",
-                r'^Given date string "a" not likely a datetime, at position 0$',
-                r'^unconverted data remains when parsing with format "%H:%M:%S": "9", '
-                f"at position 0. {PARSING_ERR_MSG}$",
-                r"^second must be in 0..59: 00:01:99, at position 0$",
+                r'^Given date string "a" not likely a datetime$',
+                r'^unconverted data remains when parsing with format "%H:%M:%S": "9". '
+                f"{PARSING_ERR_MSG}$",
+                r"^second must be in 0..59: 00:01:99$",
             ]
         )
         with pytest.raises(ValueError, match=msg):
@@ -1368,7 +1366,7 @@ def test_datetime_outofbounds_scalar(self, value, format):
             assert res is NaT
 
         if format is not None:
-            msg = r'^time data ".*" doesn\'t match format ".*", at position 0.'
+            msg = r'^time data ".*" doesn\'t match format ".*"'
             with pytest.raises(ValueError, match=msg):
                 to_datetime(value, errors="raise", format=format)
         else:
@@ -1397,12 +1395,12 @@ def test_datetime_invalid_index(self, values, format):
 
         msg = "|".join(
             [
-                r'^Given date string "a" not likely a datetime, at position 0$',
-                r'^time data "a" doesn\'t match format "%H:%M:%S", at position 0. '
+                r'^Given date string "a" not likely a datetime$',
+                r'^time data "a" doesn\'t match format "%H:%M:%S". '
+                f"{PARSING_ERR_MSG}$",
+                r'^unconverted data remains when parsing with format "%H:%M:%S": "9". '
                 f"{PARSING_ERR_MSG}$",
-                r'^unconverted data remains when parsing with format "%H:%M:%S": "9", '
-                f"at position 0. {PARSING_ERR_MSG}$",
-                r"^second must be in 0..59: 00:01:99, at position 0$",
+                r"^second must be in 0..59: 00:01:99$",
             ]
         )
         with pytest.raises(ValueError, match=msg):
@@ -1582,8 +1580,7 @@ def test_to_datetime_malformed_raise(self):
         ts_strings = ["200622-12-31", "111111-24-11"]
         msg = (
             'Parsed string "200622-12-31" gives an invalid tzoffset, which must '
-            r"be between -timedelta\(hours=24\) and timedelta\(hours=24\), "
-            "at position 0"
+            r"be between -timedelta\(hours=24\) and timedelta\(hours=24\)"
         )
         with pytest.raises(
             ValueError,
@@ -1748,7 +1745,7 @@ def test_to_datetime_month_or_year_unit_non_round_float(self, cache, unit):
         with pytest.raises(ValueError, match=msg):
             to_datetime(np.array([1.5]), unit=unit, errors="raise")
 
-        msg = r"Given date string \"1.5\" not likely a datetime, at position 0"
+        msg = r"Given date string \"1.5\" not likely a datetime"
         with pytest.raises(ValueError, match=msg):
             to_datetime(["1.5"], unit=unit, errors="raise")
 
@@ -1802,7 +1799,7 @@ def test_unit_array_mixed_nans_large_int(self, cache):
     def test_to_datetime_invalid_str_not_out_of_bounds_valuerror(self, cache):
         # if we have a string, then we raise a ValueError
         # and NOT an OutOfBoundsDatetime
-        msg = "Unknown datetime string format, unable to parse: foo, at position 0"
+        msg = "Unknown datetime string format, unable to parse: foo"
         with pytest.raises(ValueError, match=msg):
             to_datetime("foo", errors="raise", unit="s", cache=cache)
 
@@ -1938,12 +1935,9 @@ def test_to_datetime_unit_na_values(self):
     @pytest.mark.parametrize("bad_val", ["foo", 111111111])
     def test_to_datetime_unit_invalid(self, bad_val):
         if bad_val == "foo":
-            msg = (
-                "Unknown datetime string format, unable to parse: "
-                f"{bad_val}, at position 2"
-            )
+            msg = "Unknown datetime string format, unable to parse: " f"{bad_val}"
         else:
-            msg = "cannot convert input 111111111 with the unit 'D', at position 2"
+            msg = "cannot convert input 111111111 with the unit 'D'"
         with pytest.raises(ValueError, match=msg):
             to_datetime([1, 2, bad_val], unit="D")
 
@@ -2096,7 +2090,7 @@ def test_dataframe_coerce(self, cache):
 
         msg = (
             r'^cannot assemble the datetimes: time data ".+" doesn\'t '
-            r'match format "%Y%m%d", at position 1\.'
+            r'match format "%Y%m%d"\.'
         )
         with pytest.raises(ValueError, match=msg):
             to_datetime(df2, cache=cache)
@@ -2174,7 +2168,7 @@ def test_dataframe_float(self, cache):
         df = DataFrame({"year": [2000, 2001], "month": [1.5, 1], "day": [1, 1]})
         msg = (
             r"^cannot assemble the datetimes: unconverted data remains when parsing "
-            r'with format ".*": "1", at position 0.'
+            r'with format ".*": "1".'
         )
         with pytest.raises(ValueError, match=msg):
             to_datetime(df, cache=cache)
@@ -2196,7 +2190,7 @@ def test_to_datetime_barely_out_of_bounds(self):
         # in an in-bounds datetime
         arr = np.array(["2262-04-11 23:47:16.854775808"], dtype=object)
 
-        msg = "^Out of bounds nanosecond timestamp: .*, at position 0"
+        msg = "^Out of bounds nanosecond timestamp: .*"
         with pytest.raises(OutOfBoundsDatetime, match=msg):
             to_datetime(arr)
 
@@ -2231,10 +2225,7 @@ def test_to_datetime_iso8601_fails(self, input, format, exact):
         # `format` is longer than the string, so this fails regardless of `exact`
         with pytest.raises(
             ValueError,
-            match=(
-                rf"time data \"{input}\" doesn't match format "
-                rf"\"{format}\", at position 0"
-            ),
+            match=(rf"time data \"{input}\" doesn't match format " rf"\"{format}\""),
         ):
             to_datetime(input, format=format, exact=exact)
 
@@ -2253,10 +2244,9 @@ def test_to_datetime_iso8601_exact_fails(self, input, format):
         # `format` is shorter than the date string, so only fails with `exact=True`
         msg = "|".join(
             [
-                '^unconverted data remains when parsing with format ".*": ".*"'
-                f", at position 0. {PARSING_ERR_MSG}$",
-                f'^time data ".*" doesn\'t match format ".*", at position 0. '
+                '^unconverted data remains when parsing with format ".*": ".*". '
                 f"{PARSING_ERR_MSG}$",
+                f'^time data ".*" doesn\'t match format ".*". ' f"{PARSING_ERR_MSG}$",
             ]
         )
         with pytest.raises(
@@ -2297,10 +2287,7 @@ def test_to_datetime_iso8601_separator(self, input, format):
         # https://github.com/pandas-dev/pandas/issues/12649
         with pytest.raises(
             ValueError,
-            match=(
-                rf"time data \"{input}\" doesn\'t match format "
-                rf"\"{format}\", at position 0"
-            ),
+            match=(rf"time data \"{input}\" doesn\'t match format " rf"\"{format}\""),
         ):
             to_datetime(input, format=format)
 
@@ -2390,8 +2377,7 @@ def test_to_datetime_with_space_in_series(self, cache):
         # GH 6428
         ser = Series(["10/18/2006", "10/18/2008", " "])
         msg = (
-            r'^time data " " doesn\'t match format "%m/%d/%Y", '
-            rf"at position 2. {PARSING_ERR_MSG}$"
+            r'^time data " " doesn\'t match format "%m/%d/%Y". ' rf"{PARSING_ERR_MSG}$"
         )
         with pytest.raises(ValueError, match=msg):
             to_datetime(ser, errors="raise", cache=cache)
@@ -2466,7 +2452,7 @@ def test_to_datetime_strings_vs_constructor(self, result):
     def test_to_datetime_unprocessable_input(self, cache):
         # GH 4928
         # GH 21864
-        msg = '^Given date string "1" not likely a datetime, at position 1$'
+        msg = '^Given date string "1" not likely a datetime$'
         with pytest.raises(ValueError, match=msg):
             to_datetime([1, "1"], errors="raise", cache=cache)
 
@@ -2643,7 +2629,7 @@ def test_dayfirst_warnings_invalid_input(self):
             ValueError,
             match=(
                 r'^time data "03/30/2011" doesn\'t match format '
-                rf'"%d/%m/%Y", at position 1. {PARSING_ERR_MSG}$'
+                rf'"%d/%m/%Y". {PARSING_ERR_MSG}$'
             ),
         ):
             to_datetime(arr, dayfirst=True)
@@ -2714,7 +2700,7 @@ def test_to_datetime_inconsistent_format(self, cache):
         ser = Series(np.array(data))
         msg = (
             r'^time data "01-02-2011 00:00:00" doesn\'t match format '
-            rf'"%m/%d/%Y %H:%M:%S", at position 1. {PARSING_ERR_MSG}$'
+            rf'"%m/%d/%Y %H:%M:%S". {PARSING_ERR_MSG}$'
         )
         with pytest.raises(ValueError, match=msg):
             to_datetime(ser, cache=cache)
@@ -2820,7 +2806,7 @@ def test_day_not_in_month_coerce(self, cache, arg, format):
         assert isna(to_datetime(arg, errors="coerce", format=format, cache=cache))
 
     def test_day_not_in_month_raise(self, cache):
-        msg = "day is out of range for month: 2015-02-29, at position 0"
+        msg = "day is out of range for month: 2015-02-29"
         with pytest.raises(ValueError, match=msg):
             to_datetime("2015-02-29", errors="raise", cache=cache)
 
@@ -2830,34 +2816,34 @@ def test_day_not_in_month_raise(self, cache):
             (
                 "2015-02-29",
                 "%Y-%m-%d",
-                f"^day is out of range for month, at position 0. {PARSING_ERR_MSG}$",
+                f"^day is out of range for month. {PARSING_ERR_MSG}$",
             ),
             (
                 "2015-29-02",
                 "%Y-%d-%m",
-                f"^day is out of range for month, at position 0. {PARSING_ERR_MSG}$",
+                f"^day is out of range for month. {PARSING_ERR_MSG}$",
             ),
             (
                 "2015-02-32",
                 "%Y-%m-%d",
-                '^unconverted data remains when parsing with format "%Y-%m-%d": "2", '
-                f"at position 0. {PARSING_ERR_MSG}$",
+                '^unconverted data remains when parsing with format "%Y-%m-%d": "2". '
+                f"{PARSING_ERR_MSG}$",
             ),
             (
                 "2015-32-02",
                 "%Y-%d-%m",
-                '^time data "2015-32-02" doesn\'t match format "%Y-%d-%m", '
-                f"at position 0. {PARSING_ERR_MSG}$",
+                '^time data "2015-32-02" doesn\'t match format "%Y-%d-%m". '
+                f"{PARSING_ERR_MSG}$",
             ),
             (
                 "2015-04-31",
                 "%Y-%m-%d",
-                f"^day is out of range for month, at position 0. {PARSING_ERR_MSG}$",
+                f"^day is out of range for month. {PARSING_ERR_MSG}$",
             ),
             (
                 "2015-31-04",
                 "%Y-%d-%m",
-                f"^day is out of range for month, at position 0. {PARSING_ERR_MSG}$",
+                f"^day is out of range for month. {PARSING_ERR_MSG}$",
             ),
         ],
     )
@@ -3226,9 +3212,7 @@ def test_invalid_origins_tzinfo(self):
 
     def test_incorrect_value_exception(self):
         # GH47495
-        msg = (
-            "Unknown datetime string format, unable to parse: yesterday, at position 1"
-        )
+        msg = "Unknown datetime string format, unable to parse: yesterday"
         with pytest.raises(ValueError, match=msg):
             to_datetime(["today", "yesterday"])
 
@@ -3249,7 +3233,7 @@ def test_to_datetime_out_of_bounds_with_format_arg(self, format, warning):
             assert res.month == 10
             assert res.day == 10
         else:
-            msg = "unconverted data remains when parsing with format.*, at position 0"
+            msg = "unconverted data remains when parsing with format.*"
             with pytest.raises(ValueError, match=msg):
                 to_datetime("2417-10-10 00:00:00.00", format=format)
 
@@ -3473,9 +3457,7 @@ def test_to_datetime_mixed_or_iso_exact(exact, format):
 
 def test_to_datetime_mixed_not_necessarily_iso8601_raise():
     # https://github.com/pandas-dev/pandas/issues/50411
-    with pytest.raises(
-        ValueError, match="Time data 01-01-2000 is not ISO8601 format, at position 1"
-    ):
+    with pytest.raises(ValueError, match="Time data 01-01-2000 is not ISO8601 format"):
         to_datetime(["2020-01-01", "01-01-2000"], format="ISO8601")
 
 
@@ -3500,6 +3482,15 @@ def test_unknown_tz_raises():
         to_datetime([dtstr])
 
 
+def test_unformatted_input_raises():
+    valid, invalid = "2024-01-01", "N"
+    ser = Series([valid] * start_caching_at + [invalid])
+    msg = 'time data "N" doesn\'t match format "%Y-%m-%d"'
+
+    with pytest.raises(ValueError, match=msg):
+        to_datetime(ser, format="%Y-%m-%d", exact=True, cache=True)
+
+
 def test_from_numeric_arrow_dtype(any_numeric_ea_dtype):
     # GH 52425
     pytest.importorskip("pyarrow")

pandas/tests/tslibs/test_array_to_datetime.py

@@ -260,7 +260,7 @@ def test_to_datetime_barely_out_of_bounds():
     # Close enough to bounds that dropping nanos
     # would result in an in-bounds datetime.
     arr = np.array(["2262-04-11 23:47:16.854775808"], dtype=object)
-    msg = "^Out of bounds nanosecond timestamp: 2262-04-11 23:47:16, at position 0$"
+    msg = "^Out of bounds nanosecond timestamp: 2262-04-11 23:47:16$"
 
     with pytest.raises(tslib.OutOfBoundsDatetime, match=msg):
         tslib.array_to_datetime(arr)