In this tutorial, we will look at how to get a value in a Python deque by its index with the help of some examples.
deque in Python
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 a value at a specific index in a deque in Python?
Deques in Python make it very easy to add and remove elements from either end but you can also use an index to directly access an element inside the deque.
Similar to lists, deques in Python are indexed starting from 0 and you can use the
 notation to get the value at a specific index in a deque.
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The following is the syntax –
# get value at index i in deque, "queue" queue[i]
This is similar to how you’d get the value by its index in other ordered iterables (like list, tuple, string, etc.) in Python.
Let’s now look at some examples of using the above syntax
Example 1 – Get value by index in a deque
First, let’s create a deque with some elements.
from collections import deque # create a deque queue = deque([1, 2, 3]) # print the deque print(queue)
deque([1, 2, 3])
Here, we imported the
deque class from the
collections module and created a deque object,
queue with some numbers. You can see that the deque contains three values 1, 2, and 3.
To get a value by using its index in a deque, use its index inside the
 notation. For example, let’s get the value at index
1 in the above deque.
# get the value at index 1 print(queue)
We get the value at index 1 in the deque,
If you use an index outside the index range of the deque, you’ll get an
# get the value at index 3 print(queue)
--------------------------------------------------------------------------- IndexError Traceback (most recent call last) Input In , in <module> 1 # get the value at index 3 ----> 2 print(queue) IndexError: deque index out of range
Here, we’re trying to access the value at the index
3. Since the deque, here, only has values till the index
2, we get an
Example 2 – Get value by index in a bounded deque
This method works similarly for bounded deques (deques with a specified maximum size).
For example, let’s create a bounded deque and try to access an element using its index.
# create a bounded deque queue = deque([1, 2, 3], maxlen=4) # print the deque print(queue) # get the value at index 1 print(queue)
deque([1, 2, 3], maxlen=4) 2
Here, we created a bounded deque with
maxlen 4 and three elements. We then got the value at the index
1 in this bounded deque.
You might also be interested in –
- Python – Convert a deque of strings to a single string
- Python – Convert a deque to a list
- Python – Get the Index of the Maximum Value in Deque
- Python – Get the Index of the Minimum Value in Deque
- Python – Get the Maximum and the Minimum Value in a Deque
- Python – Check If a Deque is Empty
- Python – Count occurrences of a value in deque
- Python – Create a deque copy
- Python – Rotate a Deque to the Right and Left
- Python – Extend deque to the left
- Python – Extend deque to the right
- Python – Get the Max Size of a Deque
- Python – Reverse a deque
- Python – Get Index of a Value in Deque
- Python – Remove Element by Value in Deque
- Python – Remove all elements from a deque (clear deque)
- Python – Append Element to a Deque
- Python – Append Element to the Left in Deque
- Python – Pop Element From Left in Deque
- Python – Pop Element From the End in Deque
- Python – Insert Element at a given Index in Deque
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