Why this apparent assymetry in set operations?
mr.cerutti at gmail.com
Tue Jan 15 16:26:58 CET 2008
On Jan 15, 2008 10:10 AM, <skip at pobox.com> wrote:
> I've noticed that I can update() a set with a list but I can't extend a set
> with a list using the |= assignment operator.
> >>> s = set()
> >>> s.update([1,2,3])
> >>> s
> set([1, 2, 3])
> >>> s |= [4,5,6]
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> TypeError: unsupported operand type(s) for |=: 'set' and 'list'
> >>> s |= set([4,5,6])
> >>> s
> set([1, 2, 3, 4, 5, 6])
> Why is that? Doesn't the |= operator essentially map to an update() call?
No, according to 3.7 Set Types, s | t maps to s.union(t).
Neil Cerutti <mr.cerutti+python at gmail.com>
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