tomlrange

Parse and validate { from = …, to = … } tables. Not a TOML parser — feed it the dicts tomllib already produced.

The four spellings below are alternatives, not one document — a [table] header owns every following key until the next header. After tomllib, they collapse to two Python values. Bound accepts a single table. Bounds accepts a table or a list of tables.

# one table
months = { from = 1, to = 12 }

[months]
from = 1
to = 12

# many tables
windows = [
    { from = 1, to = 4 },
    { from = 6, to = 10 },
]

[[windows]]
from = 1
to = 4

[[windows]]
from = 6
to = 10

import tomllib
from tomlrange import Domain

Month = Domain(int, lo=1, hi=12, name="month")

data = tomllib.loads(config)
year = Month.bound(data["months"])  # 1..12
windows = Month.bounds(data["windows"])  # 1..4 and 6..10

assert list(year) == list(range(1, 13))
assert 5 not in windows

No runtime dependencies. Endpoints stay the type tomllib gave you.

Domain as schema

A Domain is the constraint object. Bound / Bounds are the values.

from tomlrange import Domain

Hour = Domain(int, lo=0, hi=23, name="hour")
Hour.bound({"from": 7, "to": 16})
Hour.full()  # requires lo and hi

Or name the domain by subclassing Spec — the class body is the schema:

from tomlrange import Spec


class Month(Spec):
    typ = int
    lo = 1
    hi = 12


Month.parse({"from": 1, "to": 4})
Month.parse_many([{"from": 1, "to": 4}, {"from": 6, "to": 10}])

Named discrete order is members. wrap=True is a cyclic topology — from after to walks across the seam. from == to stays a singleton; the full cycle is full().

class Weekday(Spec):
    typ = str
    members = ("mon", "tue", "wed", "thu", "fri", "sat", "sun")
    wrap = True


list(Weekday.parse({"from": "sat", "to": "mon"}))  # sat, sun, mon

Time-of-day is clock position on the 24h line, not duration. Unquoted 09:00:00 is TOML local time (datetime.time).

import tomllib
from datetime import time, timedelta

from tomlrange import Clock, elapsed

hours = Clock.parse(tomllib.loads("open = { from = 09:00:00, to = 17:00:00 }")["open"])
assert hours.as_tuple()[0].hour == 9
assert type(hours.start) is time
assert type(hours.stop) is time
assert elapsed(hours) == timedelta(hours=8)

quarter = Clock.parse(
    tomllib.loads("open = { from = 09:00:00, to = 17:00:00, step = 15 }")["open"]
)
assert quarter.step == timedelta(minutes=15)
assert quarter.domain.step == timedelta(minutes=1)

elapsed is derived walk length ((width - 1) * step) — endpoints stay time. wrap=True allows overnight { from = 22:00:00, to = 02:00:00 } (elapsed is then the wrap walk, 4 hours). A singleton is one tick, not a full day. Optional table step is a positive int count of the domain grain (Clock default one minute, so step = 15 is 15 minutes). Omit it and walk stays Domain.step, or +1 on ints.

Validation

On one table:

• value is a mapping
• keys are from and to (override with Domain(..., keys=("start", "end"))) plus optional step
• each endpoint is type(raw) is domain.typ (so 1.0 and True are not int). A time domain accepts naive datetime.time only. Aware times, dates, datetimes, timedeltas, and strings are rejected
• endpoints sit inside lo / hi when those are set
• when members is set, each endpoint is an exact member (unknown → error at from / to)
• from <= to in domain order (a singleton is { from = 3, to = 3 }); with wrap=True, from after to is a seam walk, not an error

On a list, overlap= is "reject" (default), "allow", or "merge". Reject treats a shared endpoint as overlap (1–4 and 4–6 fail). Adjacent integers (1–4 then 5–8) are fine; merge() will coalesce them. Member domains overlap and merge on member identity, not string order.

list(), len(), and width work for int, members, and datetime.time (at the bound's step when set, else Domain.step, default one minute). as_range() is int-only. Other ordered typs raise TypeError ("{name} width is only defined for int"). Membership, as_tuple(), and as_table() work for any ordered typ.

Errors carry a path:

months_ranges[1].to: 13 is above month 12

What this is not

• Not a file loader. Call tomllib yourself.
• Not string ranges ("1-12", "Jan–Apr", "9AM-5PM").
• Not a two-element array ([1, 12]). After TOML decode that is a list, not a table.
• Not wrap-around unless the domain sets wrap=True.
• Not a free-for-all str domain. Names need members.
• Not iteration over other ordered typs (walk dates yourself). Time walks at step.

Install

pip install tomlrange

Python 3.14+.