self question

[Chris Lambacher]

On Tue, Jul 25, 2006 at 08:08:32PM +0200, Sch?le Daniel wrote:
> dan.gass at gmail.com schrieb:
> >> cnt = 1
> >> def foo():
> >> 	global cnt
> >> 	cnt += 1
> >> 	return cnt
> >>
> >> def bar(x=foo()):
> >> 	print x
> >>
> >> bar()	# 2
> >> bar()	# 2
> >> bar()	# 2
> > 
> > Looks to me like you want to use the following programming pattern to
> > get dynamic default arguments:
> > 
> > cnt = 1
> > def foo():
> > 	global cnt
> > 	cnt += 1
> > 	return cnt
> > 
> > def bar(x=None):
> > 	if x is None:
> > 		x = foo()
> > 	print x
> >  
> > bar()	# 2
> > bar()	# 3
> > bar()	# 4
> 
> yes, I haven't thought of that
> nowI changed my class to
> 
> class Graph:
> 	settings = {
> 		"NumNodes" : 10,
> 		"MinNodes" : 2,
> 		"MaxNodes" : 5
> 	}
> 	def randomizeEdges(self,
> 		lowhigh = (settings["MinNodes"], settings["MaxNodes"])):
Note that this is a change in behaviour from what you originally stated you
wanted.  settings is a dictionary that is shared between all instances of
Graph.  The previous poster was suggesting the correct pattern for the
behaviour you requested.  Generally if you want a parameter to have a dynamic
default argument you set the default value to None, test for None in the body
of the function/method and set the value appropriately.
> 		low, high = lowhigh
> 		for node in self.nodes:
> 			x = random.randint(low, high)
> 			# link the nodes
> 
> 
> maybe the only minor point is that no relationship
> can be expressed
> 
> settings = {
> 	"NumNode" : 10,
> 	"MinNode" : settings["NumNode"] / 2,
> 	"MaxNode" : settings["NumNode"]
> }
> 
> but I think the solution is nevertheless ok
> 
> 
> Regards, Daniel
> -- 
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