#20743: Parent.list() should return an immutable tuple
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Reporter: jsrn | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-7.3
Component: categories | Keywords: parent, immutable
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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The current behaviour of `Parent.list()` is the road to insanity:
{{{
sage: F = GF(5)
sage: F.list()
[0, 1, 2, 3, 4]
sage: F.list().remove(0)
sage: F.list()
[1, 2, 3, 4]
}}}
The reason is that the output of `list` is cached, and a list is mutable,
and so the user can permanently modify it. This easily happens without
wanting to.
The closest Python concept of an "immutable list" is a tuple.
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Ticket URL: <http://trac.sagemath.org/ticket/20743>
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