Prefix date parser

This is a helper class to parse dates with varied degrees of precision. For example, a data source might state a date as 2001, 2001-4 or 2001-04-02, with the implication that only the year, month or day is known. This library will process such partial dates into a structured format and allow their validation and re-formatting (e.g. turning 2001-4 into 2001-04 above).

The library does not support the complexities of the ISO 8601 and RFC 3339 standards including date ranges and calendar-week/day-of-year notations.

Installation

Install prefixdate using PyPI:

$ pip install prefixdate

Usage

The library provides a variety of helper functions to parse and format partial dates:

from prefixdate import parse, normalize_date, Precision

# Parse returns a `DatePrefix` object:
date = parse('2001-3')
assert date.text == '2001-03'
date = parse(2001)
assert date.text == '2001'
assert date.precision == Precision.YEAR

date = parse(None)
assert date.text is None
assert date.precision == Precision.EMPTY
# This will also be the outcome for invalid dates!

# Normalize to a standard string:
assert normalize_date('2001-1') == '2001-01'
assert normalize_date('2001-00-00') == '2001'
assert normalize_date('Boo!') is None

# This also works for datetimes:
from datetime import datetime
now = datetime.utcnow().isoformat()
minute = normalize_date(now, precision=Precision.MINUTE)

# You can also feed in None, date and datetime:
normalize_date(datetime.utcnow())
normalize_date(datetime.date())
normalize_date(None)

You can also use the parse_parts helper, which is similar to the constructor for a datetime:

from prefixdate import parse_parts, Precision

date = parse_parts(2001, '3', None)
assert date.precision == Precision.MONTH
assert date.text == '2001-03'

Caveats

• Does not process milliseconds yet.
• Does not process invalid dates, like Feb 31st.