frozenlist
A list-like structure which implements collections.abc.MutableSequence
Decision gist · record as of 2026-08-14
Yes. FrozenList is stable, actively maintained, has zero dependencies, and solves a real problem—bridging the gap between mutable construction and immutable finalization. No security vulnerabilities. The Apache-2.0 license is permissive. Install it if you need a hashable list-like container or want to enforce immutability after initialization.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python 3.9 or later.
- Low install friction with no runtime dependencies.
- Active maintenance with recent releases and broad Python version support from 3.9 through 3.14, including PyPy.
License · maintenance · safety
Apache-2.0 (permissive) — Apache-2.0 permissive license allows commercial use, modification, and distribution with minimal restrictions.
last release 2025-10-06 (312 days) · last repo commit 2026-08-10 · 124 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 554,242,815 downloads/mo, #65 on PyPI
Alternatives
Verify before relying
pip install frozenlist
from frozenlist import FrozenList
fl = FrozenList([17, 42])
fl.append('spam')
fl.freeze()
# fl.append('more') raises RuntimeError
hash(fl) # now hashable- Performance characteristics compared to standard tuple or frozenset for typical use patterns.
- Memory overhead of the freeze mechanism relative to built-in immutable types.
What it is and what it does
FrozenList is a mutable sequence container that implements the collections.abc.MutableSequence interface. You create it with initial data, modify it freely like a normal list, then call freeze() to lock it against further changes. Once frozen, any attempt to modify the list raises RuntimeError, and the frozen list becomes hashable so it can be used as a dictionary key or set member.
The package is implemented in Cython for performance and has no runtime dependencies. It's actively maintained with wheels built for multiple Python versions (3.9–3.14) and implementations (CPython, PyPy), making installation straightforward across platforms.
Use it for
- Use as a dictionary key or set member after populating and freezing to ensure immutability.
- Build a collection incrementally during initialization, then lock it to prevent accidental modifications.
- Cache data structures that must remain unchanged after construction in multi-threaded or async contexts.
- Replace tuple when you need mutable construction followed by immutable finalization.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes.
FrozenList is stable, actively maintained, has zero dependencies, and solves a real problem—bridging the gap between mutable construction and immutable finalization. No security vulnerabilities. The Apache-2.0 license is permissive. Install it if you need a hashable list-like container or want to enforce immutability after initialization.
Install
frozenlist on PyPI
Before you install
Low install friction with no runtime dependencies. Active maintenance with recent releases and broad Python version support from 3.9 through 3.14, including PyPy.
Requires Python 3.9 or later.
License in practice
Apache-2.0 permissive license allows commercial use, modification, and distribution with minimal restrictions.
Quickstart
pip install frozenlist
from frozenlist import FrozenList
fl = FrozenList([17, 42])
fl.append('spam')
fl.freeze()
# fl.append('more') raises RuntimeError
hash(fl) # now hashableVerify before relying
- Performance characteristics compared to standard tuple or frozenset for typical use patterns.
- Memory overhead of the freeze mechanism relative to built-in immutable types.
Package facts
| License | Apache-2.0 permissive |
| Python support | Supports the current Python release >=3.9 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | None |
| Maintenance | Actively maintained 312 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 554,242,815 / month, #65 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 :: DevelopersOperating System :: MacOS :: MacOS XOperating System :: Microsoft :: WindowsOperating System :: POSIXProgramming Language :: CythonProgramming Language :: PythonProgramming Language :: Python :: 3Programming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.12Programming Language :: Python :: 3.13Programming Language :: Python :: 3.14Programming Language :: Python :: 3.9Programming Language :: Python :: Implementation :: CPythonProgramming Language :: Python :: Implementation :: PyPy |
Evidence: frozenlist-1.8.0-py3-none-any.whl
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