Title: Queues And Stacks
Slug: queues_and_stacks
Summary: Queues And Stacks in Python.
Date: 2016-01-23 12:00
Category: Python
Tags: Basics
Authors: Chris Albon

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Preliminaries



In [1]:

    
from collections import deque

Make A Queue



In [2]:

    
# Option 1: Make a queue
queue = deque(range(10))

# Option 2: Make a queue that, if full, discards any item at the 
# opposite end to where you added an item.
queue = deque(range(10), maxlen=10)

Manipulate Queue



In [3]:

    
# Append an item to the right

queue.append('A')

# View queue
queue









    Out[3]:





deque([1, 2, 3, 4, 5, 6, 7, 8, 9, 'A'])



In [4]:

    
# Append an item to the left

queue.appendleft('A')

# View queue
queue









    Out[4]:





deque(['A', 1, 2, 3, 4, 5, 6, 7, 8, 9])



In [5]:

    
# Count occurances of item
queue.count('A')

# View queue
queue









    Out[5]:





deque(['A', 1, 2, 3, 4, 5, 6, 7, 8, 9])



In [6]:

    
# Remove and return right-most item
queue.pop()

# View queue
queue









    Out[6]:





deque(['A', 1, 2, 3, 4, 5, 6, 7, 8])



In [7]:

    
# Remove and return left-most item
queue.popleft()


# View queue
queue









    Out[7]:





deque([1, 2, 3, 4, 5, 6, 7, 8])



In [8]:

    
# Insert item to the right of an item
queue.insert(2, 'A')

# View queue
queue









    Out[8]:





deque([1, 2, 'A', 3, 4, 5, 6, 7, 8])



In [9]:

    
# Reverse the queue
queue.reverse()

# View queue
queue









    Out[9]:





deque([8, 7, 6, 5, 4, 3, 'A', 2, 1])



In [10]:

    
# Delete all items
queue.clear()

# View queue
queue









    Out[10]:





deque([])