rangeslib

rangeslib is a typed Python library for eager, C++-inspired range pipelines. The public API is intentionally small:

from rangeslib import ranges, views

The mental model is:

ranges creates values
views transforms values
views.to converts the final result

Quick Start

from rangeslib import ranges, views

result = (
    ranges.iota(1, 11)
    | views.filter(lambda value: value % 2 == 0)
    | views.transform(lambda value: value * 10)
    | views.take(3)
    | views.to(list)
)

assert result == [20, 40, 60]

Range values are eager and reusable. Most adaptors return another Range; the terminal views.to(...) adaptor returns whatever collection or factory you ask for.

Existing Iterables

Ordinary Python iterables can start pipelines too:

from rangeslib import views

text = "abcdef" | views.take(3) | views.to(str)
assert text == "abc"

chars = "abc" | views.all()
assert list(chars) == ["a", "b", "c"]

views.all() is the eager Python counterpart to C++ views::all: it adapts an existing iterable into a reusable Range.

Reusable Pipelines

Adaptors can be composed before data is supplied:

from rangeslib import views

first_three_even = views.filter(lambda value: value % 2 == 0) | views.take(3)

assert list([1, 2, 3, 4, 5, 6] | first_three_even) == [2, 4, 6]
assert list([10, 11, 12, 14] | first_three_even) == [10, 12, 14]

Sources And Views

The ranges facade creates source ranges:

from rangeslib import ranges

ranges.empty()
ranges.single("value")
ranges.iota(1, 5)
ranges.indices(3)
ranges.repeat("x", 3)

The views facade contains transformations such as:

all, reverse, filter, transform, take, drop, counted,
elements, keys, values, enumerate, concat, zip, cartesian_product,
adjacent, pairwise, chunk, slide, stride, join, split, to

See docs/usage.md for the full API catalog.

C++ Ranges Correspondence

rangeslib borrows naming and broad behavior from C++20/23/26 ranges, but it is not a lazy C++ view implementation. The most important differences are:

• Python iterables replace C++ iterator/sentinel pairs.
• Range stores eager values instead of reference-like lazy views.
• Tuple results are ordinary Python tuples, not tuples of references.
• Python type checking is useful but cannot express every C++ tuple-like rule.

See docs/cpp-comparison.md for details.

Installation

Python 3.12 or newer is required.

python -m pip install .

For development:

python -m pip install -e ".[dev]"

rangeslib has no runtime dependencies.

The 1.x series preserves the documented Range, ranges, and views public API. Private modules and implementation classes are not part of the compatibility contract; breaking public changes require a new major version.

Development

Useful commands live in scripts/:

./scripts/run_tests.sh       # tests only
./scripts/typecheck.sh       # mypy + Pyright
./scripts/check.sh           # Ruff, typing, tests, coverage
./scripts/check_all.sh       # check.sh + strict Sphinx docs
./scripts/check_package.sh   # sdist/wheel build and install smoke test
./scripts/run_playground.sh  # manual playground

Before a release commit, run:

./scripts/check_all.sh
./scripts/check_package.sh

Documentation

Build the Sphinx site with:

./scripts/generate_docs.sh

Generated HTML is written to docs/_build/html/ and published to GitHub Pages after CI succeeds on main.

Releases

Changing [project].version in pyproject.toml on main automatically runs the complete quality and package checks, then creates the matching Git tag and GitHub Release and publishes the distribution to PyPI through Trusted Publishing after the PyPI project is configured.

For future work, prefer opening or collecting issues before adding more adaptors immediately. See docs/roadmap.md.

See docs/publishing.md for the PyPI setup checklist.