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Troubleshooting

qddate fails closed: unsupported or malformed input returns None instead of raising. This page covers the usual reasons and how to inspect a miss.

parse() returns None​

Check these in order:

  1. The date is not at the start of the string. published 12.03.1999 does not match; 12.03.1999 published does.
  2. The format is not in the catalog. Rare layouts need a new pattern. See adding languages.
  3. The language was excluded. DateParser(languages="en") will not parse Russian month names.
  4. The calendar date is invalid. Month 13, day 0, or a non-existent day becomes None.
  5. The string is too short or empty. "", whitespace, and "1" return None.

Inspect the matched pattern​

When a parse succeeds but looks wrong, inspect match():

result = parser.match(text)
if result is None:
    print("no pattern matched")
else:
    print(result["pattern"]["key"])
    print(result["pattern"].get("name"))
    print(dict(result["values"]))

A language you requested is missing​

languages= is an allow-list. Automatic language detection is only a candidate filter and must not drop a language you passed in. If a German or Dutch shared month name (Juli) fails under languages=["de"], that is a bug — please open an issue.

Unsupported codes raise at construction:

qddate.DateParser(languages="xx")
# ValueError: Unsupported language(s): ['xx']

Ambiguous numeric dates​

01.02.2003 is day-month-year in the numeric catalog, not US month-day-year. US-style mm/dd/yyyy lives on English patterns (date_usa). Restrict languages="en" if you need that reading, or prefer unambiguous ISO strings.

Import or dependency errors​

  • Runtime: pyparsing>=3.1.0 only.
  • ModuleNotFoundError: dateparser means a benchmark script is running without the bench extra: pip install -e ".[bench]".
  • Python older than 3.8 is not supported.

Disable filters while debugging​

If you believe a pattern exists but is filtered out, turn filters off one at a time:

parser.parse(text, noprefix=True, nocharsetfilter=True, nolanguagefilter=True)

If it then matches, the miss is a filter issue rather than a missing pattern. Leave filters on in production.

Still stuck​

  • Reproduce with a short script and the exact input string.
  • Include OS, Python version, and qddate.__version__.
  • Open an issue at github.com/ivbeg/qddate/issues.