manufacturing.lot-number

def lot_number(production_date: str, line: int, sequence: int) -> str

from fune.manufacturing.lot_number import lot_number  # manufacturing.lot-number@^1

from .dates_add_days import days_from_civil, parse_iso_date  ← from dates.add-days ^1.0.0 · built alongside by fune


def lot_number(production_date: str, line: int, sequence: int) -> str:
    """Lot code YYDDD-LL-SSS: two-digit year, day of the year, line, sequence.

    The day of the year counts from the epoch-day kernel in dates.add-days, so
    leap years move every date after 28 February without a month table.
    """
    if isinstance(line, bool) or not isinstance(line, int) or line < 1 or line > 99:
        raise ValueError("line must be a whole number from 1 to 99, received %r" % (line,))
    if isinstance(sequence, bool) or not isinstance(sequence, int) or sequence < 1 or sequence > 999:
        raise ValueError("sequence must be a whole number from 1 to 999, received %r" % (sequence,))
    date = parse_iso_date(production_date)
    day_of_year = days_from_civil(date.year, date.month, date.day) - days_from_civil(date.year, 1, 1) + 1
    return "%02d%03d-%02d-%03d" % (date.year % 100, day_of_year, line, sequence)

Install

fune build

With that line in your source, in a Python project (language python in fune.project), fune build resolves it and its 1 dependency, pins them in fune.lock, downloads only the Python package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. Or pin a range in fune.project and build in one step:

fune add manufacturing.lot-number

The manifest, vectors and README with only the Python implementation. Install it without the registry with fune add ./manufacturing.lot-number-1.0.0-python.fune, or fetch it from a terminal with fune pull manufacturing.lot-number@1.0.0:python.

The whole function, every language, is one file too: manufacturing.lot-number-1.0.0.fune, 9,136 bytes, sha256 677f36c5f07cbd03dd5a9615041db4a2d68ec3e1c5752e068bb8cee7b9982c12. It installs into a project of any language.

# fune: before manufacturing.lot-number

# fune: after manufacturing.lot-number

# fune: replace dates.add-days in manufacturing.lot-number

# fune: step manufacturing.lot-number after <n|label>

More from the author

- `YY` - the last two digits of the year - `DDD` - the day of the year, 001 to 365 (366 in a leap year): the "Julian date" printed on food, drink and pharmaceutical packs - `LL` - the production line, 01 to 99 - `SSS` - the lot's sequence number on that line that day, 001 to 999

So lot 12 on line 3 on 1 March 2026 is `26060-03-012`, and the same lot a year earlier, in a leap year, would be `24061-03-012` on 1 March 2024: 29 February moves every later day of the year by one, which is the mistake a hand-built month table makes.

**Deterministic.** The code depends only on its three arguments. The function never reads the clock and never counts: the caller owns the sequence (from the database row that records the lot) and passes the date the lot was made. The same arguments always give the same code, so a code can be regenerated for a recall.

**Fixed width.** Every code is 12 characters, so codes sort by date within a century, then line, then sequence, and fit a fixed field on a label.

**Two-digit years repeat every century.** `26060` is 1 March 2026 and 1 March 2126. Lots are not kept that long, but the code is not a date to parse back without context.

"Julian date" here is the day-of-year convention used on packaging, not the astronomical Julian Day Number. Day numbers come from `dates.add-days`, so leap years follow the full Gregorian rule (2000 was a leap year, 1900 was not).

A line outside 1-99, a sequence outside 1-999, or a date that does not exist (2026-02-30) is an error rather than a code that would not fit the format.

Files