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 }])

Validation

On one table:

• value is a mapping
• keys are exactly from and to (override with Domain(..., keys=("start", "end")))
• each endpoint is type(raw) is domain.typ (so 1.0 and True are not int)
• endpoints sit inside lo / hi when those are set
• from <= to (a singleton is { from = 3, to = 3 })

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.

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").
• Not a two-element array ([1, 12]). After TOML decode that is a list, not a table.
• Not wrap-around (from = 11, to = 2). Write two spans.
• Not step. A range table is a closed interval.

Install

pip install tomlrange

Python 3.12+.