PythonArraysBeginner

list.pop()

Removes and returns an item (default last) from a list (mutates).

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item = my_list.pop(index=-1)
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What it does

Overview

Removes and returns an item (default last) from a list (mutates).

The list.pop([index]) method removes the item at the specified position in a list and returns its value. If no index is provided, pop() defaults to the last item (index -1). In terms of algorithmic complexity, popping from the end of a list is an O(1) operation, making lists efficient for stack implementations (Last-In-First-Out). However, popping from the front (index 0) or the middle is an O(n) operation because Python must shift all subsequent elements one position to the left to maintain a contiguous array. This method modifies the original list in-place and raises an IndexError if the list is empty or the index is out of bounds.

Quick reference

Syntax

item = my_list.pop(index=-1)

Inputs

Parameters

index (optional)int · Index to remove; default -1 (last).

See it in practice

Examples

1

Stack Behavior (LIFO)

stack = ['action1', 'action2', 'action3']
last_action = stack.pop()

print(last_action)
print(stack)
Output:
action3 ['action1', 'action2']

Calling pop() without arguments removes and returns the last element, mimicking a stack.

2

Removing at Specific Index

tasks = ['email', 'code', 'review', 'test']
completed = tasks.pop(1)

print(completed)
print(tasks)
Output:
code ['email', 'review', 'test']

Passing an index allows you to remove an element from a specific position. Note that items to the right of 'code' are shifted left.

3

Using the Returned Value

items = [10, 20, 30]
while items:
    current = items.pop()
    print(f'Processing {current}')
Output:
Processing 30 Processing 20 Processing 10

Since pop() returns the element, it is commonly used in loops to consume a list until it is empty.

Debug faster

Common Errors

1

IndexError

Cause: Attempting to pop from an empty list.

Fix: Check if the list is not empty before calling pop(), or use a try-except block.

data = []
if data:
    data.pop()
else:
    print('List is empty')
2

IndexError

Cause: Providing an index that exceeds the current list range.

Fix: Ensure the index is within the valid range of -len(list) to len(list) - 1.

items = ['a', 'b']
items.pop(5)  # Raises IndexError

Runtime support

Compatibility

Python 3.8+

Source: MDN Web Docs

Common questions

Frequently Asked Questions

Removes and returns an item (default last) from a list (mutates).

index: Index to remove; default -1 (last).

IndexError: Check if the list is not empty before calling pop(), or use a try-except block. IndexError: Ensure the index is within the valid range of -len(list) to len(list) - 1.