[Tutor] recursive memory (for Q 1)

[Lloyd Kvam]

I have made this same mistake.
def walk(t, f, a, visited={}):
visited is given a clean dictionary only ONCE, when the function is
defined.  If you call walk a second time, without specifying visited,
you will simply default to using the same dictionary again.

One solution is:
def walk(t, f, a, visited=None):
	if visited is None: visited = {}

This provides a clean dictionary everytime walk is called without the
visited argument.

I can't help on Q2.

Christopher Smith wrote:

> I'm making a modification to the walk() function on the Mac so it avoids
> getting caught in an alias loop between folders (i.e. walking a folder
> which has an alias to another folder which has an alias of the first
> folder).  The way I do this is store the file specs in a dictionary.  I
> have two questions.
> 
> 1)
> Here's what I'm doing:
> 
> macpath module
> --------------
> def walk(t, f, a, visited={}):
> 	.
> 	.
> 	.
> 	for file in listOfFiles:
> 		.
> 		.
> 		.
> 		if visited.has_key(filespec): continue
> 		visited[filespec]=''
> 		t=join(t,file)
> 		walk(t, f, a, visited) # I pass the modified dictionary
> 
> #demo
> walk(t, f, a) #no dictionary sent so it should start at {}
> 
> I need the dictionary to start at {} every time I first give the walk, but
> then want it updated as I go deeper in the walk--so the main script call
> leaves the dictionary off but recursive calls send the modified
> dictionary.  Is this the right way to go about this?
> 
> 2) 
> I would also like to find out if an alias points to another (unmounted)
> volume.  The only problem is that if the volume is unmounted, the
> ResolveAliasFile routine (or other routines that will give file
> information, like mac.stat()) will prompt me to insert the volume; I would
> like to have the walk be unattended and so would like a way to override
> the insert volume reaction and just know that the alias points to an
> unmounted volume and just skip it.  Is there another way to detect this
> condition without being asked to insert the missing volume?
> 
> /c
> 
> 
> 
> 
> _______________________________________________
> Tutor maillist  -  Tutor@python.org
> http://mail.python.org/mailman/listinfo/tutor
> 
> 


-- 
Lloyd Kvam
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