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Immutable/hashable numpy Array
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| # ISC License (ISC) | |
| # | |
| # Copyright 2021 Christopher Fuller | |
| # | |
| # Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, | |
| # provided that the above copyright notice and this permission notice appear in all copies. | |
| # THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL | |
| # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, | |
| # INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER | |
| # IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR | |
| # PERFORMANCE OF THIS SOFTWARE. | |
| from numpy import ndarray, asarray | |
| class ImmutArray(ndarray): | |
| """https://numpy.org/doc/stable/user/basics.subclassing.html | |
| >>> import numpy as np | |
| >>> a=np.arange(4) | |
| >>> ia=ImmutArray(a) | |
| >>> (ia==[0,1,2,3]).all().item() | |
| True | |
| >>> (ia==(0,1,2,3)).all().item() | |
| True | |
| >>> ((0,1,2,3)==ia).all().item() | |
| True | |
| >>> ([0,1,2,3]==ia).all().item() | |
| True | |
| >>> (ia==range(4)).all().item() | |
| True | |
| >>> (range(4)==ia).all().item() | |
| True | |
| >>> a[1]=-1 | |
| >>> a | |
| array([ 0, -1, 2, 3]) | |
| >>> (a==ia).all().item() | |
| False | |
| >>> (ia==a).all().item() | |
| False | |
| >>> ia[1]=-1 | |
| Traceback (most recent call last): | |
| File "<stdin>", line 1, in <module> | |
| ValueError: assignment destination is read-only | |
| >>> ia | |
| ImmutArray([0, 1, 2, 3]) | |
| >>> (np.arange(4)==ia).all().item() | |
| True | |
| >>> (ia==np.arange(4)).all().item() | |
| True | |
| >>> ib=ia[1:3] | |
| >>> ib | |
| ImmutArray([1, 2]) | |
| >>> ib[0]=9 | |
| Traceback (most recent call last): | |
| File "<stdin>", line 1, in <module> | |
| ValueError: assignment destination is read-only | |
| >>> ia=np.arange(4).view(ImmutArray) | |
| >>> ia[0]=9 | |
| Traceback (most recent call last): | |
| File "<stdin>", line 1, in <module> | |
| ValueError: assignment destination is read-only | |
| """ | |
| def __new__(cls, arr): | |
| obj = asarray(arr).copy().view(cls) | |
| obj.flags.writeable = False | |
| obj._hash = cls._gethash(obj) | |
| return obj | |
| def __array_finalize__(self, obj): | |
| if obj is None: | |
| return | |
| self._hash = getattr(obj, '_hash', None) or self._gethash(obj) | |
| self.flags.writeable = False | |
| @staticmethod | |
| def _gethash(arr): | |
| return hash((arr.shape, tuple(arr.flat))) | |
| def __hash__(self): | |
| return self._hash | |
| __eq__ = ndarray.__eq__ | |
| if __name__ == '__main__': | |
| import doctest | |
| results = doctest.testmod() | |
| if results.attempted: | |
| if results.failed: | |
| print('Failure!') | |
| else: | |
| print('Success!') | |
| else: | |
| print('No tests found!') |
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Oh, I think the hashing is broken: