Colin J. Williams
1/15/2008 3:54:00 PM
Neil Cerutti wrote:
> On Jan 15, 2008 10:10 AM, <skip@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).
>
If the RHS is a set then it works OK:
*** Python 2.5.1 (r251:54863, Apr 18
2007, 08:51:08) [MSC v.1310 32 bit
(Intel)] on win32. ***
>>> import sets
>>> s1= sets.Set([2, 4, 5])
Set([2, 4, 5])
>>> s1= sets.Set([2, 4, 5])
>>> s2= sets.Set([4, 5, 6])
>>> s1|s2
Set([2, 4, 5, 6])
>>> s1|=s2
>>> s1
Set([2, 4, 5, 6])
>>>
It could be modifies to handle any
iterable on the RHS.
Colin W.