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slice not hashable #84783
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slice cannot be hashed which make some operations significantly more annoying. see https://groups.google.com/forum/#!topic/comp.lang.python/SvhkWwSDeIw |
Please re-upload the patch file as an uncompressed text file, as it is quite difficult for many people to view zip files in their browser. |
This is a reasonable use case. +1 for making slice() hashable. Will, you're welcome to submit a PR. If not, I'm sure someone else would be happy to scoop this up :-) |
Would be happy to help with this. Sent a PR soon ;) |
I think slices were explicitly made not hashable to avoid issues to avoid issues with dictionaries, see discussion at https://mail.python.org/pipermail/python-list/2001-March/076101.html and bpo-408326. The commit that did this is a1351fb Is this not needed anymore? Wouldn't this need to be discussed on python-ideas? |
Guido, what are your thoughts on this proposal? On the one hand, the OP has a legitimate use case:
On the other hand, slice literals for mappings are a mixed bag, possibly useful in some cases, possibly surprising in others:
I like the idea of being able to cache array or sequence slices but worry about opening a can of worms for the general case. |
I think this is fine. The "danger" of d[a:b] seems overstated, it produces a clear KeyError. |
@gvanrossum Thanks for the looking at this. |
Note that this still needs a “what’s new” entry, since it is a new feature and might even trip some folks up (see the test changes needed). |
* main: (60 commits) pythongh-102056: Fix a few bugs in error handling of exception printing code (python#102078) pythongh-102011: use sys.exception() instead of sys.exc_info() in docs where possible (python#102012) pythongh-101566: Sync with zipp 3.14. (pythonGH-102018) pythonGH-99818: improve the documentation for zipfile.Path and Traversable (pythonGH-101589) pythongh-88233: zipfile: handle extras after a zip64 extra (pythonGH-96161) pythongh-101981: Apply HOMEBREW related environment variables (pythongh-102074) pythongh-101907: Stop using `_Py_OPCODE` and `_Py_OPARG` macros (pythonGH-101912) pythongh-101819: Adapt _io types to heap types, batch 1 (pythonGH-101949) pythongh-101981: Build macOS as recommended by the devguide (pythonGH-102070) pythongh-97786: Fix compiler warnings in pytime.c (python#101826) pythongh-101578: Amend PyErr_{Set,Get}RaisedException docs (python#101962) Misc improvements to the float tutorial (pythonGH-102052) pythongh-85417: Clarify behaviour on branch cuts in cmath module (python#102046) pythongh-100425: Update tutorial docs related to sum() accuracy (FH-101854) Add missing 'is' to `cmath.log()` docstring (python#102049) pythongh-100210: Correct the comment link for unescaping HTML (python#100212) pythongh-97930: Also include subdirectory in makefile. (python#102030) pythongh-99735: Use required=True in argparse subparsers example (python#100927) Fix incorrectly documented attribute in csv docs (python#101250) pythonGH-84783: Make the slice object hashable (pythonGH-101264) ...
* main: (225 commits) pythongh-102056: Fix a few bugs in error handling of exception printing code (python#102078) pythongh-102011: use sys.exception() instead of sys.exc_info() in docs where possible (python#102012) pythongh-101566: Sync with zipp 3.14. (pythonGH-102018) pythonGH-99818: improve the documentation for zipfile.Path and Traversable (pythonGH-101589) pythongh-88233: zipfile: handle extras after a zip64 extra (pythonGH-96161) pythongh-101981: Apply HOMEBREW related environment variables (pythongh-102074) pythongh-101907: Stop using `_Py_OPCODE` and `_Py_OPARG` macros (pythonGH-101912) pythongh-101819: Adapt _io types to heap types, batch 1 (pythonGH-101949) pythongh-101981: Build macOS as recommended by the devguide (pythonGH-102070) pythongh-97786: Fix compiler warnings in pytime.c (python#101826) pythongh-101578: Amend PyErr_{Set,Get}RaisedException docs (python#101962) Misc improvements to the float tutorial (pythonGH-102052) pythongh-85417: Clarify behaviour on branch cuts in cmath module (python#102046) pythongh-100425: Update tutorial docs related to sum() accuracy (FH-101854) Add missing 'is' to `cmath.log()` docstring (python#102049) pythongh-100210: Correct the comment link for unescaping HTML (python#100212) pythongh-97930: Also include subdirectory in makefile. (python#102030) pythongh-99735: Use required=True in argparse subparsers example (python#100927) Fix incorrectly documented attribute in csv docs (python#101250) pythonGH-84783: Make the slice object hashable (pythonGH-101264) ...
GH-102548 adds the missing What's New entry. |
What's New was merged, so I think this can be closed |
Will Bradshaw contributed original patch on bpo-40603. --------- Co-authored-by: Terry Jan Reedy <[email protected]>
…ble) (python#103146) Will Bradshaw contributed original patch on bpo-40603. --------- Co-authored-by: Terry Jan Reedy <[email protected]>
Thank you for fixing this. For anyone who was wanting hashable slices, my library ndindex may be of interest. It has a hashable |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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