fix: parse ordinal tokens in from_format, raise ValueError for the rest

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Change Log
 
+## Unreleased
+
+### Fixed
+- `from_format` now parses the ordinal tokens `Mo`, `Qo` and `DDDo`, and `Do` in locales without ordinal suffixes, matching what `format()` emits; the remaining unsupported ordinal tokens raise the regular `ValueError` instead of `AttributeError` [#1074](https://github.com/python-pendulum/pendulum/issues/1074)
+
 ## [3.3.0] - 2026-10-12
 
 ### Added

src/pendulum/formatting/formatter.py

@@ -45,6 +45,20 @@
 _MATCH_TIMEZONE = "[A-Za-z0-9-+]+(/[A-Za-z0-9-+_]+)?"
 
 
+def _ordinal_candidates(locale: Locale, plain_fallback: bool = True) -> tuple[str, ...]:
+    """Regex candidates matching `format()` output for ordinal tokens.
+
+    Locales without a `custom.ordinal` table format ordinals as plain
+    numbers (see `Locale.ordinalize`), so the pattern must accept bare
+    digits there.
+    """
+    ordinals = locale.get("custom.ordinal")
+    if not ordinals:
+        return (r"\d+",) if plain_fallback else ()
+
+    return tuple(rf"\d+{o}" for o in ordinals.values())
+
+
 class Formatter:
     _TOKENS: str = (
         r"\[([^\[]*)\]|\\(.)|"
@@ -71,14 +85,12 @@ class Formatter:
     _LOCALIZABLE_TOKENS: ClassVar[
         dict[str, str | Callable[[Locale], Sequence[str]] | None]
     ] = {
-        "Qo": None,
+        "Qo": lambda locale: _ordinal_candidates(locale),
         "MMMM": "months.wide",
         "MMM": "months.abbreviated",
-        "Mo": None,
-        "DDDo": None,
-        "Do": lambda locale: tuple(
-            rf"\d+{o}" for o in locale.get("custom.ordinal").values()
-        ),
+        "Mo": lambda locale: _ordinal_candidates(locale),
+        "DDDo": lambda locale: _ordinal_candidates(locale),
+        "Do": lambda locale: _ordinal_candidates(locale),
         "dddd": "days.wide",
         "ddd": "days.abbreviated",
         "dd": "days.short",
@@ -630,6 +642,24 @@ def _get_parsed_locale_value(
         elif token == "Do":
             parsed["day"] = int(cast("Match[str]", re.match(r"(\d+)", value)).group(1))
 
+            return
+        elif token == "Qo":
+            parsed["quarter"] = int(
+                cast("Match[str]", re.match(r"(\d+)", value)).group(1)
+            )
+
+            return
+        elif token == "Mo":
+            parsed["month"] = int(
+                cast("Match[str]", re.match(r"(\d+)", value)).group(1)
+            )
+
+            return
+        elif token == "DDDo":
+            parsed["day_of_year"] = int(
+                cast("Match[str]", re.match(r"(\d+)", value)).group(1)
+            )
+
             return
         elif token == "dddd":
             unit = "day_of_week"
@@ -676,6 +706,9 @@ def _replace_tokens(self, token: str, locale: Locale) -> str:
 
         if token in self._LOCALIZABLE_TOKENS:
             values = self._LOCALIZABLE_TOKENS[token]
+            if values is None:
+                raise ValueError(f"Unsupported token: {token}")
+
             if callable(values):
                 candidates = values(locale)
             else:

tests/datetime/test_from_format.py

@@ -220,3 +220,37 @@ def test_from_format_2_digit_year():
 
     d = pendulum.from_format("99", "YY")
     assert d.year == 1999
+
+
+def test_from_format_do_ordinal():
+    d = pendulum.from_format("7th June 1982", "Do MMMM YYYY", locale="en")
+    assert_datetime(d, 1982, 6, 7)
+
+
+def test_from_format_do_without_locale_ordinals():
+    # de has no custom.ordinal table; format() emits the plain number
+    d = pendulum.from_format("7 Juni 1982", "Do MMMM YYYY", locale="de")
+    assert_datetime(d, 1982, 6, 7)
+
+
+def test_from_format_quarter_ordinal():
+    d = pendulum.from_format("2nd 1982", "Qo YYYY", locale="en")
+    assert d.year == 1982
+    assert d.quarter == 2
+
+
+def test_from_format_month_ordinal():
+    d = pendulum.from_format("6th 1982", "Mo YYYY", locale="en")
+    assert_datetime(d, 1982, 6, 1)
+
+
+def test_from_format_day_of_year_ordinal():
+    d = pendulum.from_format("158th 1982", "DDDo YYYY", locale="en")
+    assert_datetime(d, 1982, 6, 7)
+
+
+@pytest.mark.parametrize("token", ["do", "e", "eo", "Wo", "wo"])
+def test_from_format_unsupported_tokens_raise_value_error(token):
+    # previously a raw AttributeError leaked from the None entries
+    with pytest.raises(ValueError, match="Unsupported token"):
+        pendulum.from_format(f"1 1982", f"{token} YYYY", locale="en")