Python appendleft()

The appendleft() method adds an element to the left end (front) of a collections.deque object. This is useful for managing elements in a queue-like structure, where items are added and removed from opposite ends.

Syntax

deque.appendleft(element)

Parameters:

• element: The item to add to the left end (front) of the deque.

Return value:

• None. The deque is modified in place.

Example: Adding elements to the left side of a deque using appendleft()

In this example, appendleft() adds elements to the left end of a deque, demonstrating how items are prepended to the front:

from collections import deque

# Create a deque
my_deque = deque([1, 2, 3])
print(f"Initial deque: {my_deque}")

# Append an element to the left
my_deque.appendleft(0)
print(f"Deque after appendleft(0): {my_deque}")

# Append another element
my_deque.appendleft(-1)
print(f"Deque after appendleft(-1): {my_deque}")

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The output of this code is:

Initial deque: deque([1, 2, 3])
Deque after appendleft(0): deque([0, 1, 2, 3])
Deque after appendleft(-1): deque([-1, 0, 1, 2, 3])

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Codebyte Example: Using appendleft() for Dynamic Queue Operations

In this example, appendleft() is used to add elements to the front of a deque, simulating dynamic queue operations where new items arrive at the front:

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