The popleft() method of deque class

Method signature:

popleft()

Parameters:

None

Return value:

Returns the removed element.

Overview:

A deque Python is double ended queue. Elements can be added and removed from either side of the deque.
The popleft() method removes an element from the left side of the deque and returns the element.
Invoking popleft() on an empty deque raises an exception of type IndexError.

Example:

# Example Python program that removes an element
# from a Python deque
import collections

# Create a deque
numberDeque = collections.deque((20, 40, 60, 80))
print("Deque elements before invoking popleft():")
print(numberDeque)

# Remove an element from the left of the deque
element = numberDeque.popleft()

print("The popleft() call removed the element:{}".format(element))

print("Deque elements after invoking popleft():")
print(numberDeque)

Output:

Deque elements before invoking popleft():
deque([20, 40, 60, 80])
The popleft() call removed the element:20
Deque elements after invoking popleft():
deque([40, 60, 80])