Python List extend() - Adds Iterables to List
The extend() method adds all the items from the specified iterable (list, tuple, set, dictionary, string) to the end of the list.
Syntax:
list.extend(iterable)Parameters:
iterable: Any iterable (list, tuple, set, string, dict)
Return type:
No return value.
The following example demonstrates the extend() method.
Example: extend()
cities = ['Mumbai', 'London', 'Paris', 'New York']
newCities = ['Delhi', 'Chicago']
cities.extend(newCities)
print("Updated List: ", cities)
Output
Updated List: ['Mumbai', 'London', 'Paris', 'New York', 'Delhi', 'Chicago']
The following adds a tuple elements to a list.
Example: Add Tuple Elements
cities = ['Mumbai', 'London', 'Paris', 'New York']
cities_tup = ('Delhi','Chicago')
cities.extend(cities_tup)
print("Updated List: ", cities)
Output
Updated List: ['Mumbai', 'London', 'Paris', 'New York', 'Delhi', 'Chicago']
The following adds a set elements to a list.
Example: Add Set Elements
cities = ['Mumbai', 'London', 'Paris', 'New York']
cities_set = {'Delhi','Chicago'}
cities.extend(cities_set)
print("Updated List: ",cities)
Output
Updated List: ['Mumbai', 'London', 'Paris', 'New York', 'Delhi', 'Chicago']
The following adds a dictionary keys to list.
Example: Add Dictionary Keys
cities = ['Mumbai', 'London', 'Paris', 'New York']
capitals = {'New Delhi':'India','Washington DC':'USA'}
cities.extend(capitals) # adds keys of dict as elements
print("Updated List: ",cities)
Output
Updated List: ['Mumbai', 'London', 'Paris', 'New York', 'New Delhi', 'Washington DC']
Extend Iterable Using the + Operator
The + operator can also be used to extend the iterable objects. However, it can only be used with the same type of iterables e.g. adding list to list, tuple to tuple.
Example: Append Using + Operator
cities = ['Mumbai', 'London']
favcities = ['Paris', 'New York']
cities = cities + favcities # or cities += favcities
print("Cities: ", cities)
Output
Cities: ['Mumbai', 'London', 'Paris', 'New York']extend() vs append()
The extend() method adds items of the specified iterable at the end of the list, whereas the append() method adds the whole iterable as an item at the end of the list.
Example: extend() vs append()
cities = ['Mumbai', 'London']
bigcities = ['Washington DC', 'Banglore']
favcities = ['Paris', 'New York']
cities.extend(favcities)
bigcities.append(favcities)
print("Cities: ", cities)
print("Big Cities: ", bigcities)
Output
Cities: ['Mumbai', 'London', 'Paris', 'New York']
Big Cities: ['Washington DC', 'Banglore', ['Paris', 'New York']]