collections-extended
Extra Python Collections - bags (multisets) and setlists (ordered sets)
Decision gist · record as of 2026-08-14
Yes, if you need one of these specialized collection types and can accept that the package will not receive updates. The code is stable, has no dependencies, and works with current Python versions. No, if you require active maintenance or plan to rely on future bug fixes—consider whether the standard library or a maintained alternative meets your needs instead.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python >=3.7,<4.0; Python 2 is not supported.
- Installation is frictionless—a pure Python wheel with no runtime dependencies.
- However, the package is marked abandoned with no commits since 2023-03-12 and no releases for over a year, so expect no maintenance or bug fixes going forward.
License · maintenance · safety
Apache-2.0 (permissive) — Licensed under Apache-2.0 (permissive), which allows commercial and private use with minimal restrictions—suitable for most projects without legal concern.
last release 2022-01-23 (1664 days) · last repo commit 2023-03-12 · 47 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 731,821 downloads/mo, #5,204 on PyPI
Alternatives
Verify before relying
pip install collections-extended
from collections_extended import bag, setlist, bijection, IndexedDict
b = bag('abracadabra')
print(b.count('a')) # 5
sl = setlist('abracadabra')
print(sl[0]) # 'a'
bij = bijection({'a': 1, 'b': 2})
print(bij.inverse[1]) # 'a'
idict = IndexedDict()
idict['key'] = 'value'
print(idict.get(index=0)) # 'value'- Performance characteristics compared to standard dict/set for large datasets
- Real-world adoption patterns and whether abandonment poses practical risk for your use case
What it is and what it does
collections_extended is a pure Python library that adds four specialized collection types to Python's standard library. It provides bag (a multiset that tracks element counts), setlist (an ordered set combining list indexing with set uniqueness), bijection (a bidirectional one-to-one mapping), and IndexedDict (a dictionary that also supports integer index access). Each type has a frozen (hashable) variant. The library has no external dependencies and works with Python 3.6, 3.7, 3.8, 3.9, 3.10 and PyPy3.
The package is useful when you need collections with specific semantics that the standard library doesn't provide—for instance, when you need to count occurrences of items like a Counter but with removal semantics, or when you need both fast membership testing and positional access like a set and a list combined. However, the project is no longer maintained: the last release was 2022-01-23 and the last commit 2023-03-12, so it will not receive updates or bug fixes.
Use it for
- Track element frequencies with removal: use bag when you need multiset semantics with count() and remove() operations.
- Maintain insertion order with uniqueness: use setlist when you need a list that forbids duplicates and supports fast membership testing.
- Bidirectional key-value mapping: use bijection when you need to look up values by key and keys by value interchangeably.
- Access dictionary entries by position: use IndexedDict when you need both key-based and index-based access to an ordered mapping.
- Range-based lookups: use RangeMap to map contiguous ranges (dates, numbers) to values and query which range contains a given point.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes, if you need one of these specialized collection types and can accept that the package will not receive updates.
The code is stable, has no dependencies, and works with current Python versions. No, if you require active maintenance or plan to rely on future bug fixes—consider whether the standard library or a maintained alternative meets your needs instead.
Install
collections-extended on PyPI
Before you install
Installation is frictionless—a pure Python wheel with no runtime dependencies. However, the package is marked abandoned with no commits since 2023-03-12 and no releases for over a year, so expect no maintenance or bug fixes going forward.
Requires Python >=3.7,<4.0; Python 2 is not supported.
License in practice
Licensed under Apache-2.0 (permissive), which allows commercial and private use with minimal restrictions—suitable for most projects without legal concern.
Quickstart
pip install collections-extended
from collections_extended import bag, setlist, bijection, IndexedDict
b = bag('abracadabra')
print(b.count('a')) # 5
sl = setlist('abracadabra')
print(sl[0]) # 'a'
bij = bijection({'a': 1, 'b': 2})
print(bij.inverse[1]) # 'a'
idict = IndexedDict()
idict['key'] = 'value'
print(idict.get(index=0)) # 'value'Verify before relying
- Performance characteristics compared to standard dict/set for large datasets
- Real-world adoption patterns and whether abandonment poses practical risk for your use case
Package facts
| License | Apache-2.0 permissive |
| Python support | Supports the current Python release >=3.7,<4.0 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | None |
| Maintenance | Abandoned 1,664 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 731,821 / month, #5,204 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 5 - Production/StableIntended Audience :: DevelopersLicense :: OSI Approved :: Apache Software LicenseOperating System :: OS IndependentProgramming Language :: PythonProgramming Language :: Python :: 3Programming Language :: Python :: 3.10Programming Language :: Python :: 3.6Programming Language :: Python :: 3.7Programming Language :: Python :: 3.8Programming Language :: Python :: 3.9Programming Language :: Python :: Implementation :: PyPyTopic :: Software DevelopmentTopic :: Software Development :: LibrariesTopic :: Software Development :: Libraries :: Python Modules |
Evidence: collections_extended-2.0.2-py3-none-any.whl
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See also jaraco.collections · multiset · sortedcollections · ordered-set · frozenlist · sortedcontainers · immutables · frozendict · itypes · orderly-set