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What is the best queue implemetation in Python?


I want to write a code for Breadth First Traveral for Graph, which needs a
queue to implement.

I wonder that for such a powerful language as Python, whether there is a
better and simpler implementation for a traditional FIFO queue?

Thanks!

On Feb 23, 11:12 am, "John" <rds1@sh163.net> wrote:

> I want to write a code for Breadth First Traveral for Graph, which needs a
> queue to implement.

> I wonder that for such a powerful language as Python, whether there is a
> better and simpler implementation for a traditional FIFO queue?

Better and simpler than *WHAT*?
Than C or PASCAL
I mean, list or dictionary in Python are so powerful than the traditional
array. Maybe I can make use of it?

"John Machin" <sjmac@lexicon.net> wrote in message

news:1172190018.915043.200560@v45g2000cwv.googlegroups.com...

On Feb 23, 11:24 am, "John" <rds1@sh163.net> wrote:

> Than C or PASCAL
> I mean, list or dictionary in Python are so powerful than the traditional
> array. Maybe I can make use of it?

Well, you could wite your own queue manager using Python lists,
but ...

You have this strange reluctance to look in the documentation. Have
you tried Google? Try http://docs.python.org/lib/deque-objects.html

Or perhaps you want/need the Queue module or the heapq module.

*You* find them and *you* work out what is best for *your* needs.

If you have a question that you could not answer yourself, then ask it
here.

HTH,
John

John Machin wrote:
> On Feb 23, 11:12 am, "John" <rds1@sh163.net> wrote:
>> I want to write a code for Breadth First Traveral for Graph, which needs
>> a queue to implement.

>> I wonder that for such a powerful language as Python, whether there is a
>> better and simpler implementation for a traditional FIFO queue?

> Better and simpler than *WHAT*?

Sorry, but you do that all the time ... "ask the question as you know the
answer, otherwise shut the f u ..."

Can't you assume for a second that other people do not have your wonderful
brain and still have to make it through 60+ years of life of learning ?

hg

hg wrote:
> f u

"f o" of course

John wrote:
> I want to write a code for Breadth First Traveral for Graph, which needs a
> queue to implement.

> I wonder that for such a powerful language as Python, whether there is a
> better and simpler implementation for a traditional FIFO queue?

For a BFS I coded up a while back iterating over a list of nodes (and
appending nodes to the list as dictated by the algorithm) did the job.

Duncan

You could do yourself a favor and not answer. You would also be sparing
the rest of us your rude tone.

James

John:

> I want to write a code for Breadth First Traveral for Graph, which needs a
> queue to implement.

For that purpose I have used the good deque that you can find in
collections in the standard library. It's very good for queues, and
it's a bit faster than regular lists for stacks too.

Bye,
bearophile

> For that purpose I have used the good deque that you can find in
> collections in the standard library. It's very good for queues, and
> it's a bit faster than regular lists for stacks too.

you mean *much* faster (since a list is a reference array so pop(0) is
O(n) operation)

never use a list as queue if len(queue) > 10000

=== benchmark

$ time ./deque_queue.py
34359607296

real    0m0.286s
user    0m0.264s
sys     0m0.016s

$ time ./list_queue.py
34359607296

real    1m20.915s
user    1m18.649s
sys     0m0.396s

=== the sources

--- deque_queue.py:
#!/usr/bin/python2.5

from collections import deque

def f(n):
        sum = 0
        queue = deque()
        for i in range(n):
                queue.append(i)
        while queue:
                sum += queue.popleft()
        print sum

if __name__=='__main__':
        f(1<<18)

--- list_queue.py:
#!/usr/bin/python2.5

def f(n):
        sum = 0
        queue = list()
        for i in range(n):
                queue.append(i)
        while queue:
                sum += queue.pop(0)
        print sum

if __name__=='__main__':
        f(1<<18)

On Feb 22, 12:40 pm, hg <h@nospam.org> wrote:

Um... first off, you have to admit that a lot of what is posted
on the internet in general and even on groups like this is rambling,
poorly thought out, missing necessary context, and just generally a
mess and hard to understand.

So maybe a little peer pressure on folks to clean up their posts and
try
to express themselves clearly isn't such a bad thing.

And finally, let's face it: if the internet ever does cease to be a
place
where you can see crotechety know-it-all programmers roasting clueless
noobs,
then, honestly, what is the point of owning a computer?

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