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Python lists have 11 built-in methods for adding, removing, finding, reordering, and copying items. The crucial choices are whether you’re working with one value or an iterable, removing by value or position, and changing a list in place or creating a new one.
Python list methods at a glance
The method behavior below follows the Python 3.14.7 tutorial. Most methods change the existing list and return None; the main exception for removal is pop(), which returns the removed item. Python documentation: Data Structures
| Method | Use | Result or failure behavior |
|---|---|---|
append(x) |
Add one item to the end | Changes the list; returns None |
extend(iterable) |
Add each item from an iterable to the end | Changes the list; returns None |
insert(i, x) |
Insert an item before index i |
Changes the list; returns None |
remove(x) |
Remove the first item equal to x |
Changes the list; raises ValueError if no match exists |
pop([i]) |
Remove and retrieve the item at index i; defaults to the last item |
Returns the removed item; raises IndexError for an empty list or invalid index |
clear() |
Remove all items | Changes the list; returns None |
index(x[, start[, stop]]) |
Find the first matching item, optionally searching a range | Returns its index in the whole list; raises ValueError if absent |
count(x) |
Count items equal to x |
Returns an integer |
sort(key=None, reverse=False) |
Sort the list in place | Changes the list; returns None |
reverse() |
Reverse the current order | Changes the list; returns None |
copy() |
Create a shallow copy | Returns a new outer list; nested objects are shared |
How do you add items to a list?
Use append() for one item
append(x) adds its argument as a single element at the end. If the argument is itself a list, that list becomes one nested element:
items = ["pen", "book"]
items.append(["tape", "glue"])
# ["pen", "book", ["tape", "glue"]]
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Use extend() for items from an iterable
extend(iterable) adds the iterable’s elements individually. For example, items.extend(["tape", "glue"]) adds two strings to the end rather than adding a nested list. This distinction matters whenever the argument is a collection. Python documentation: Data Structures
Use insert() for a position
insert(i, x) places x before index i. For example, items.insert(1, "notebook") puts the new item before the element currently at index 1. Use append() when the destination is simply the end.
How do you remove an item?
Remove by value with remove()
remove(x) deletes the first item equal to x. If the list contains duplicates, later matching items remain. If there is no equal item, Python raises ValueError.
Remove by position and keep the value with pop()
pop(i) removes and returns the item at index i. With no argument, pop() removes and returns the last item. It raises IndexError if the list is empty or the requested index is invalid.
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clear() removes all items from the existing list. It is different from assigning a new empty list when other variables refer to the same list: clearing changes the shared object.
How do you find or count list values?
Find a position with index()
index(x) returns the index of the first item equal to x. You can supply start and stop to limit the search: index(x, start, stop). The returned position is still measured from the beginning of the whole list, not from the start of the search range. If no match is found, Python raises ValueError.
Count matches with count()
count(x) returns the number of items equal to x, including zero when there are no matches.
How do you reorder a list?
Sort the existing list with sort()
sort() changes the list in place. It accepts an optional key function for determining sort order and reverse=True for descending order. For example, names.sort(key=str.lower) sorts strings using their lowercase forms as the keys. The elements must be orderable under the comparison or key being used.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchDo not assign the result of sort() to a variable expecting a sorted list: it returns None. The Python tutorial explains that methods such as sort() that only modify a list have no return value printed because “they return the default None.” Python documentation: Data Structures
Keep the original order with sorted()
Use the built-in sorted(a) when you need a new sorted list and want to preserve a. Like sort(), sorted() can use key and reverse arguments.
Reverse the current order with reverse()
reverse() reverses the items’ current order in place; it does not sort them. Like other in-place list methods, it returns None.
Does list.copy() make a deep copy?
No. copy() creates a new outer list, but it is a shallow copy: references to nested mutable objects are shared between the original and the copy. Changing the outer list does not change the other outer list, but modifying a shared nested object is visible through both. Python documentation: Data Structures
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Quick Recap
Which method should you choose?
- Add a single value at the end:
append(). - Add each value from an iterable:
extend(). - Insert before a particular index:
insert(). - Delete the first matching value:
remove(). - Delete an item by index and retrieve it:
pop(). - Find the first match or count matches:
index()orcount(). - Change the list’s order:
sort()orreverse(). - Get a sorted result without changing the input:
sorted(). - Make a shallow outer-list copy:
copy().
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