append() and extend() in Python
Append: Adds its argument as a single element to the end of a list. The length of the list increases by one.
syntax: # Adds an object (a number, a string or a # another list) at the end of my_list my_list.append(object)
my_list = ['geeks', 'for'] my_list.append('geeks') print my_list |
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Output:
['geeks', 'for', 'geeks']
NOTE: A list is an object. If you append another list onto a list, the first list will be a single object at the end of the list.
my_list = ['geeks', 'for', 'geeks'] another_list = [6, 0, 4, 1] my_list.append(another_list) print my_list |
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Output:
['geeks', 'for', 'geeks', [6, 0, 4, 1]]
extend(): Iterates over its argument and adding each element to the list and extending the list. The length of the list increases by number of elements in it’s argument.
syntax: # Each element of an iterable gets appended # to my_list my_list.extend(iterable)
my_list = ['geeks', 'for'] another_list = [6, 0, 4, 1] my_list.extend(another_list) print my_list |
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Output:
['geeks', 'for', 6, 0, 4, 1]
NOTE: A string is an iterable, so if you extend a list with a string, you’ll append each character as you iterate over the string.
my_list = ['geeks', 'for', 6, 0, 4, 1] my_list.extend('geeks') print my_list |
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Output:
['geeks', 'for', 6, 0, 4, 1, 'g', 'e', 'e', 'k', 's']
Time Complexity:
Append has constant time complexity i.e.,O(1).
Extend has time complexity of O(k). Where k is the length of list which need to be added.
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