Priority Queue in python

Question

I am adding data in priority queue in the form of (priority,data) but when I use the function get(), I get back my priority instead of data. Also, if I add in the form of (data,priority), it is sorted by data values.

here is my trial code

from Queue import PriorityQueue
q= PriorityQueue(0)
q.put(4,8)
q.put(3,7)
q.put(2,6)
q.put(1,5)
while not q.empty():
    item = q.get()[1]
    print item,
print

q= PriorityQueue(0)
q.put(4,5)
q.put(3,6)
q.put(2,7)
q.put(1,8)
while not q.empty():
    item = q.get()[1]
    print item,
print

first one is giving error TypeError: 'int' object is not iterable and second one TypeError: 'int' object has no attribute 'getitem'

Please add your code so far

A.J. Uppal
– A.J. Uppal

2014-03-02 03:48:46 +00:00
Commented Mar 2, 2014 at 3:48 — A.J. Uppal
– A.J. Uppal, Commented Mar 2, 2014 at 3:48

score 5 · Accepted Answer · 2014-03-02 04:06:34Z

5

A priority queue works like a standard queue except that the items are tuples of priority, item, so get() on such a queue will return that kind of tuple - if you want to get the actual item you should use either this which will give you both the item and its priority :

prio, item = queue.get()

Or directly like this if you don't care about the priority at all :

item = queue.get()[1]

See the official Python documentation for more info.

Edit: your comment shows that you put the values in your queue with put(4, 8), so you're only putting 4 and the 8 becomes the block argument of put() - you need to put a tuple like so :

queue.put((4, 8))

edited Mar 2, 2014 at 4:06

answered Mar 2, 2014 at 3:54

user2629998

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3 Comments

Ruturaj Over a year ago

first one is giving error TypeError: 'int' object is not iterable and second one TypeError: 'int' object has no attribute 'getitem' here is my trial code from Queue import PriorityQueue q= PriorityQueue(0) q.put(4,8) q.put(3,7) q.put(2,6) q.put(1,5) while not q.empty(): item = q.get()[1] print item, print q= PriorityQueue(0) q.put(4,5) q.put(3,6) q.put(2,7) q.put(1,8) while not q.empty(): item = q.get()[1] print item, print

user2629998 Over a year ago

@Ruturaj what error ? Edit your question and add your error and your code. Also are you sure that your queue is actually a PriorityQueue and not something else ?

chtenb Over a year ago

Items are not necessarily tuples of the form (priority, data). Items may be any comparable object.

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