priority queue problem in python

Question

I have a priority queue class that has only few functions like, if it is empty or not, push and pop an itme into it. But I need to check if a partuclar item is present in the queue or not? how would I do that??

Answer 1

If you are storing the queue items in a List inside your class you could just search the list. There are many ways to do this.

>> list = ["item1", "item2", "item3"]
["item1", "item2", "item3"]

>> matches = filter(lambda x: x == "item2", list)
["item2"]

>> count = len(b)
1

>> found = len(b) > 0
True

Also

>> list.count("item2")
1

>> list.index("item3")
2

Hope it helps. Otherwise you could post some code if you want more specific help.

Answer 2

I don't kno which type of priority queue, you use but you amy be interested by heapq in teh standard lib : http://docs.python.org/library/heapq.html

It makes possible to use a priority queue in the same way you use a list:

from heapq import heappush
l = []
heappush(l, 'D')
heappush(l, 'B')
heappush(l, 'A')

print l
>>> ['A', 'B', 'D'] 

UPDATE: When using the priority queue as a list, you can use the 'in' statement

print 'B' in l
>>> True
print 'C' in l
>>> False

Answer 3

If you are using the heapq from the standard library (and thus lists to represent your queue), you can use the in operator:

if item in myqueue:
   print "yay!"