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frozenlist @ PyPI

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frozenlist.FrozenList is a list-like structure which implements 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'}


$ pip install frozenlist

The library requires Python 3.8 or newer.


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  • Python >= 3.8


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.