Python add list element
last modified January 29, 2024
In this article we show how to add elements to a list in Python.
Python list
In Python, a list is an ordered collection of values. A list can contain various types of values. A list is a mutable container, which means that we can add values, delete values, or modify existing values.
The values of a list are called items or elements of the list. A list can contain duplicate elements. Each occurrence is considered a distinct item.
There are several ways of adding elements to list in Python:
- append method
- insert method
- extend method
- assignment operation
Python add list element with append
The append method adds an item to the end of the list.
#!/usr/bin/python vals = [1, 2, 3, 4] vals.append(5) vals.append(6) print(vals)
We have a list of integer values. We add new elements to the list with
append.
vals.append(5) vals.append(6)
Two values are added at the end of the list. The append is a
built-in method of the list container.
$ ./append_method.py [1, 2, 3, 4, 5, 6]
Python add list element with insert
The insert method inserts an element at the specified position. The
first argument of the function is the index of the element before which to
insert.
#!/usr/bin/python vals = [1, 2, 3, 4] vals.insert(0, -1) vals.insert(1, 0) vals.insert(len(vals), 5) print(vals)
In the example, we insert three new elements to a list.
vals.insert(0, -1)
We insert the -1 value at the beginning of the list. Remember that Python lists are indexed from 0.
vals.insert(len(vals), 5)
We insert the 5 value at the end of the list. This is equivalent to
append. To get the lenght of the list, we use the len
method.
$ ./insert_method.py [-1, 0, 1, 2, 3, 4, 5]
Python add list element with extend
The extend method appends all the items from the specified
iterable.
#!/usr/bin/python vals = [1, 2, 3, 4] nums = [5, 6, 7] vals.extend(nums) print(vals)
In the example, we add elements from the nums list to the
vals list.
$ ./extend_method.py [1, 2, 3, 4, 5, 6, 7]
Python add list element with assignment
We can add new elements with the assignment operation.
#!/usr/bin/python vals = [1, 2, 3, 4] vals[len(vals):] = [5] vals[len(vals):] = [6] print(vals)
The value on the right side of the assignment must be an iterable.
$ ./assignment.py [1, 2, 3, 4, 5, 6]
Source
Python data structures - language reference
In this article we have shown how to add elements to a list in Python.
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