A Q. on pop().

[spencer]

Hi,
The code.

def buildStackMajor ():
for node in dirStackMinor:
#print 's is the node...', node
dirStackMajor.a ppend(node)
dirStackMinor.p op()
print 'POP the stack...', len(dirStackMin or)
print 'after pop...', dirStackMinor

When I start the "for" loop I have 11 members in
the stack- a list. The pop() is poping member
from the back, as though it's deal with a LIFO
stack instead of LIFO. I never get pass a length
of 5.
first Q.. Why is pop() starting from the back
back of the stack?
second Q.. Why can't I never empty the stack?
Thanks.

[Duncan Booth]

Re: A Q. on pop().

spencer wrote:
[color=blue]
> first Q.. Why is pop() starting from the back
> back of the stack?[/color]

Because that is what it does. Try reading the documentation:
[color=blue][color=green][color=darkred]
>>> help(list.pop)[/color][/color][/color]
Help on method_descript or:

pop(...)
L.pop([index]) -> item -- remove and return item at index (default
last)

[color=blue]
> second Q.. Why can't I never empty the stack?[/color]

Because you are modifying a list while iterating over it which is never a
good idea. What you have now pops items from the end of the loop so it
stops about half way along. If you change it to pop item 0 then it will
shift the items down and your iteration will end up skipping over about
half of them.

Try something like this:

def buildStackMajor ():
while dirStackMinor:
dirStackMajor.a ppend(dirStackM inor.pop(0))

although in that case you might just as well get rid of the loop entirely:

dirStackMajor += dirStackMinor
del dirStackMinor[:]