# Python – Count occurrences of a value in deque

In this tutorial, we will look at how to count the frequency of a value in a deque in Python with the help of some examples.

## `deque` in Python

The `collections` module in Python comes with a `deque` class that you can use to implement a stack or queue data structure in Python. Deques support thread-safe, memory efficient appends and pops from either side of the deque with approximately the same O(1) performance in either direction.

In simple terms, you can think of a `deque` in Python as a list-like data structure but with efficient insertion and removal of items from either end (left and right). This makes them very useful when implementing a stack or queue functionality in Python.

## How to get element frequency in a deque in Python?

The `deque` class comes with a number of built-in functions to help perform common operations (like adding and removing elements).

To count the occurrences of a value in a deque in Python, use the deque `count()` function. Pass the value as an argument.

The following is the syntax –

```# count occurrences of "x" in deque "queue"
queue.count(x)```

It returns the number of elements in the deque that are equal to `x`.

## Examples

Let’s now look at some examples of using the above syntax –

### Example 1 – Count occurrences of a value deque

First, let’s create a deque with some elements.

```from collections import deque

# create a deque
queue = deque([1, 2, 3, 4, 3, 5, 7])
# print the deque
print(queue)```

Output:

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

Here, we imported the `deque` class from the `collections` module and created a deque object, `queue` with some numbers. You can see that the number `3` occurs two times in the above deque.

Now, let’s now count the occurrences of the value `3` in the above deque using code.

```# count occurrences of 3
print(queue.count(3))```

Output:

`2`

Here, we used the deque `count()` function to get the frequency of the value `3` in the above deque. It returns `2` which is the number of times `3` occurs in the deque, `queue`.

### Example 2 – Count occurrences of a value not present in a deque

Let’s now try to find the frequency of a value not present in the deque.

We’ll use the same deque from above and pass `6` as the argument (the value `6` is not present in the deque).

```# count occurrences of 6
print(queue.count(6))```

Output:

`0`

We get 0 as the output because there are no values equal to `6` in the given deque object.

You might also be interested in –

• 