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from collections import deque

class Queue:
    def __init__(self):
        self.queue = deque()

    def enqueue(self, item):
        pass

    def dequeue(self):
        if not self.is_empty():
            return self.queue.popleft()
        return "The queue is empty"

    def is_empty(self):
        return len(self.queue) == 0

queue = Queue()

queue.enqueue('A')
queue.enqueue('B')
queue.enqueue('C')

print("queue.dequeue():", queue.dequeue())
print("queue.dequeue():", queue.dequeue())
print("queue.dequeue():", queue.dequeue())

# Queue: First In, First Out Data Structure

A Queue is a **data structure where the first data entered is the first one to be removed**, following the `First In, First Out (FIFO)` principle.

It operates similarly to standing in a queue in daily life, where data is processed in order.

Queues are used in situations like job scheduling, where several tasks are queued to be processed in the order they were requested, or in printer task queues.

<br />

## Key Operations of Queue

Based on the FIFO principle, a queue offers the following key operations:

1. `Enqueue`: **Add an element** to the back (tail) of the queue. The newly added element will occupy the last position in the queue.

2. `Dequeue`: **Remove and return an element** from the front (head) of the queue. Once removed, the next element occupies the new front.

3. `Peek or Front`: **Check the element at the front** of the queue. The checked element remains in place.

4. `IsEmpty`: **Check if the queue is empty**. Returns `True` if there are no elements in the queue, otherwise `False`.

<br />

## How is a Queue Implemented?

In Python, a simple queue can be implemented using a list. However, for efficiency, the `deque` class from the `collections` module is generally used.

`deque` is a data structure that allows appending or popping elements from both ends efficiently.

```python title="Queue Implementation Example"
# Importing the deque class from collections module
from collections import deque

# Create a queue
queue = deque()

# Enqueue operations
queue.append('A')  # Add A
queue.append('B')  # Add B

# Dequeue operations
print(queue.popleft())  # Output and remove 'A'
print(queue.popleft())  # Output and remove 'B'
```

You can explore a more detailed example of implementing a queue using a `Class` in the code editor on the right.

Among the main operations of a queue, Peek or Front allows viewing the element at the very front of the queue without removing it. This operation is useful for checking the current state of the queue.

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