Introduction

frozenlist.FrozenList is a list-like structure which implements collections.abc.MutableSequence. The list is mutable until FrozenList.freeze is called, after which list modifications raise RuntimeError:

>>> from frozenlist import FrozenList
>>> fl = FrozenList([17, 42])
>>> fl.append('spam')
>>> fl.append('Vikings')
>>> fl
<FrozenList(frozen=False, [17, 42, 'spam', 'Vikings'])>
>>> fl.freeze()
>>> fl
<FrozenList(frozen=True, [17, 42, 'spam', 'Vikings'])>
>>> fl.frozen
True
>>> fl.append("Monty")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "frozenlist/_frozenlist.pyx", line 97, in frozenlist._frozenlist.FrozenList.append
    self._check_frozen()
  File "frozenlist/_frozenlist.pyx", line 19, in frozenlist._frozenlist.FrozenList._check_frozen
    raise RuntimeError("Cannot modify frozen list.")
RuntimeError: Cannot modify frozen list.

FrozenList is also hashable, but only when frozen. Otherwise it also throws a RuntimeError:

>>> fl = FrozenList([17, 42, 'spam'])
>>> hash(fl)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "frozenlist/_frozenlist.pyx", line 111, in frozenlist._frozenlist.FrozenList.__hash__
    raise RuntimeError("Cannot hash unfrozen list.")
RuntimeError: Cannot hash unfrozen list.
>>> fl.freeze()
>>> hash(fl)
3713081631934410656
>>> dictionary = {fl: 'Vikings'} # frozen fl can be a dict key
>>> dictionary
{<FrozenList(frozen=True, [1, 2])>: 'Vikings'}

Installation

$ pip install frozenlist

The library requires Python 3.8 or newer.

Documentation

https://frozenlist.aio-libs.org

Communication channels

We have a Matrix Space #aio-libs-space:matrix.org which is also accessible via Gitter.

Requirements

• Python >= 3.8

License

frozenlist is offered under the Apache 2 license.

Source code

The project is hosted on GitHub

Please file an issue in the bug tracker if you have found a bug or have some suggestions to improve the library.

Packaging updates and notes for downstreams

• Declared Python 3.12 and PyPy 3.8-3.10 supported officially in the distribution package metadata.

  Related issues and pull requests on GitHub: #553.

• Replaced the packaging is replaced from an old-fashioned setup.py to an in-tree PEP 517 build backend – by @webknjaz.

  Whenever the end-users or downstream packagers need to build frozenlist from source (a Git checkout or an sdist), they may pass a config_settings flag pure-python. If this flag is not set, a C-extension will be built and included into the distribution.

  Here is how this can be done with pip:

  $ python3 -m pip install . --config-settings=pure-python=

  This will also work with -e | --editable.

  The same can be achieved via pypa/build:

  $ python3 -m build --config-setting=pure-python=

  Adding -w | --wheel can force pypa/build produce a wheel from source directly, as opposed to building an sdist and then building from it.

  Related issues and pull requests on GitHub: #560.

Contributor-facing changes

• It is now possible to request line tracing in Cython builds using the with-cython-tracing PEP 517 config setting – @webknjaz.

  This can be used in CI and development environment to measure coverage on Cython modules, but is not normally useful to the end-users or downstream packagers.

  Here’s a usage example:

  $ python3 -Im pip install . --config-settings=with-cython-tracing=true

  For editable installs, this setting is on by default. Otherwise, it’s off unless requested explicitly.

  The following produces C-files required for the Cython coverage plugin to map the measurements back to the PYX-files:

  $ python -Im pip install -e .

  Alternatively, the FROZENLIST_CYTHON_TRACING=1 environment variable can be set to do the same as the PEP 517 config setting.

  Related issues and pull requests on GitHub: #560.

• Coverage collection has been implemented for the Cython modules – by @webknjaz.

  It will also be reported to Codecov from any non-release CI jobs.

  Related issues and pull requests on GitHub: #561.

• A step-by-step Release Guide guide has been added, describing how to release frozenlist – by @webknjaz.

  This is primarily targeting the maintainers.

  Related issues and pull requests on GitHub: #563.

• Detailed Contributing Guidelines on authoring the changelog fragments have been published in the documentation – by @webknjaz.

  Related issues and pull requests on GitHub: #564.

Bugfixes

• Removed an unused typing.Tuple import #411

Deprecations and Removals

• Dropped Python 3.7 support. #413

Misc

• #410, #433

Bugfixes

• Do not install C sources with binary distributions. #250

Deprecations and Removals

• Dropped Python 3.6 support #274