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list.remove()

Removes the first occurrence of a value from a list (mutates).

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my_list.remove(value)
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What it does

Overview

Removes the first occurrence of a value from a list (mutates).

The list.remove() method performs an in-place modification of a list by deleting the first encountered element that matches the provided value based on equality (__eq__). It is important to note that this is not an identity check (is), but a value comparison. Because the operation requires a linear scan starting from index 0 to find the match, the time complexity is O(n), where n is the length of the list. This makes it inefficient for large datasets or for use within nested loops. The method returns None; it does not return the list or the removed item. If the specified value is not present in the list, a ValueError exception is raised, necessitating defensive programming such as membership testing or exception handling blocks.

Quick reference

Syntax

my_list.remove(value)

Inputs

Parameters

valueAny · Value to remove (first occurrence).

See it in practice

Examples

1

Removing a Specific String

programming_languages = ['Python', 'Java', 'C++', 'Ruby']
programming_languages.remove('Java')
print(programming_languages)
Output:
['Python', 'C++', 'Ruby']

The first occurrence of 'Java' is found and removed, shifting subsequent elements to the left.

2

Handling Duplicate Values

numbers = [10, 20, 30, 20, 40]
numbers.remove(20)
print(numbers)
Output:
[10, 30, 20, 40]

Only the first occurrence of 20 (at index 1) is removed. The second occurrence remains in the list.

3

Safe Removal with Membership Check

items = ['keyboard', 'mouse', 'monitor']
target = 'webcam'

if target in items:
    items.remove(target)
else:
    print(f'{target} not found in list')
print(items)
Output:
webcam not found in list ['keyboard', 'mouse', 'monitor']

Using the 'in' operator prevents a ValueError when the item might not exist in the collection.

Debug faster

Common Errors

1

ValueError

Cause: Attempting to remove a value that is not present in the list.

Fix: Check if the item exists using the 'in' keyword before removal, or wrap the call in a try-except block.

data = [1, 2, 3]
data.remove(4) # Raises ValueError: list.remove(x): x not in list
2

LogicError

Cause: Removing items from a list while iterating over it with a for loop, which causes the internal index to skip items.

Fix: Iterate over a shallow copy of the list or use a list comprehension to create a new filtered list.

nums = [1, 2, 3, 4]
for n in nums:
    nums.remove(n)
# Result is [2, 4], not [] because the iterator skips indices after removal

Runtime support

Compatibility

Python 3.8+

Source: MDN Web Docs

Common questions

Frequently Asked Questions

Removes the first occurrence of a value from a list (mutates).

value: Value to remove (first occurrence).

ValueError: Check if the item exists using the 'in' keyword before removal, or wrap the call in a try-except block. LogicError: Iterate over a shallow copy of the list or use a list comprehension to create a new filtered list.