list.insert
Insert an item into the list before the given index.
Python 3.13
list.insert(i, x)Parameters
- iint
- The index before which the item goes; if it exceeds the length of the list, the item is added to the end.
- xAny
- The item to insert.
Return value
Nothing (None); the list is changed in place.
Examples
Inserting an item at an index
Python 3.13
a = [1, 3]
a.insert(1, 2)
print(a)[1, 2, 3]
Inserting at the beginning
Python 3.13
a = [1, 2]
a.insert(0, 0)
print(a)[0, 1, 2]
Details
A negative index counts from the end: a.insert(-1, x) puts the item before the last one. Inserting at the beginning shifts all items, so it is slow for a long list; for frequent inserts at the front, use collections.deque.