x, = y (???)

kj socyl at 987jk.com.invalid
Fri Jul 18 17:49:49 CEST 2008


In <BZr*yX+hs at news.chiark.greenend.org.uk> Matthew Woodcraft <mattheww at chiark.greenend.org.uk> writes:

>kj wrote:
>> I still don't get it.  If we write 
>>
>>  y  = 'Y'
>>  x, = y
>>
>> what's the difference now between x and y?  And if there's no
>> difference, what's the point of performing such "unpacking"?

>If y really is is a string, I think it's likely that the line you came
>across was a typo.


OK, this is the best explanation I've seen for the code I'm talking about.

This code may be found at:

  http://norvig.com/sudo.py

in the definition of the function eliminate.  Here's the fragment:

    elif len(values[s]) == 1:
        ## If there is only one value (d2) left in square, remove it from peers
        d2, = values[s]

Now, in the assignment, values[s] *is* a string of length 1.  So
this assignment appears to me entirely equivalent (in its ultimate
effect) to the more straightforward

        d2 = values[s]

...but, since I'm a noob, I thought I'd ask :-)

Thanks!

kynn
-- 
NOTE: In my address everything before the first period is backwards;
and the last period, and everything after it, should be discarded.



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