How to check queue length in Python

Question

How to check Queue\'s length in python?

I dont see they provide Queue.lenght in python....

http://docs.python.org/tutorial/datastructures.html

fr         


        

Answer 1

Use queue.rear+1 to get the length of the queue

Answer 2

it is simple just use .qsize() example:

a=Queue()
a.put("abcdef")
print a.qsize() #prints 1 which is the size of queue

The above snippet applies for Queue() class of python. Thanks @rayryeng for the update.

for deque from collections we can use len() as stated here by K Z.

Answer 3

Yes we can check the length of queue object created from collections.

from collections import deque
class Queue():
    def __init__(self,batchSize=32):
        #self.batchSie = batchSize
        self._queue = deque(maxlen=batchSize)

    def enqueue(self, items):
        ''' Appending the items to the queue'''
        self._queue.append(items)

    def dequeue(self):
        '''remoe the items from the top if the queue becomes full '''
        return self._queue.popleft()

Creating an object of class

q = Queue(batchSize=64)
q.enqueue([1,2])
q.enqueue([2,3])
q.enqueue([1,4])
q.enqueue([1,22])

Now retrieving the length of the queue

#check the len of queue
print(len(q._queue)) 
#you can print the content of the queue
print(q._queue)
#Can check the content of the queue
print(q.dequeue())
#Check the length of retrieved item 
print(len(q.dequeue()))

check the results in attached screen shot

Hope this helps...

Answer 4

len(queue) should give you the result, 3 in this case.

Specifically, len(object) function will call object.__len__ method [reference link]. And the object in this case is deque, which implements __len__ method (you can see it by dir(deque)).

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queue= deque([])   #is this length 0 queue?

Yes it will be 0 for empty deque.