updating a variable / scope problem

[Rajarshi Guha]

On Thu, 08 Jul 2004 13:32:55 -0700, Robert Brewer wrote:

> Rajarshi Guha wrote:
>> def f(x):
>> 
>>     print 'hello'
>>     c  =0
>> 
>>     def g(y):
>>         print c
>>         c = c + 1
>>         print 'bye'
>>     
>>     g(10)
>> 
>> if __name__ == "__main__":
>>     f(5)
>> 
>> running it gives me an error:
>> UnboundLocalError: local variable 'c' referenced before assignment
>> 
> Once you add the line "c = c + 1", you've told Python that c should be
> local to g(), since it involves a binding (assignment). It is *possible*
> to get around this with, for example:
> 
Aah, thanks. I'm basically converting Bron and Kerbosch's clique detection
algorithm to  python. The described algorithm is basically :

def clique( .. ):
   def extend( .. ):
     ..
     ..
     if ( .. ) extend( .. )
     ..
     ..

   c = 0
   ..
   extend( .. )

The variable c is accessed in the function extend().

I suppose I could just make c and argument to extend as you mention -
though it seems a little less elegent than allowing extend() to have
access to c directly.

Thanks,
Rajarshi