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Aya Bouchiha
Aya Bouchiha

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This Is Your Complete Guide To All Python List Methods

#python #programming #beginners #codenewbie

Hi, I'm Aya Bouchiha, today, I'm going to talk about the list of built-in objects.

Definition of a List

A list is a mutable, iterable, ordered collection of values. It is used to store different and multiple values in one variable.

Creating a list 

new_list = ['hi', 1, False, {"name":"Aya"}, [10, 20], None] print(new_list) # ['hi', 1, False, {"name":"Aya"}, [10, 20], None] print(type(new_list)) # <class 'list'> print(len(new_list)) # 6
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All list methods

append()

append(value): this list method lets you insert an element at the end of the list.

my_list = [10, 20, 30] my_list.append(40) print(my_list.append(50)) # None  print(my_list) # [10, 20, 30, 40, 50]  my_list.append() # error
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insert()

insert(index, value): used to add a new element at a given index

admins = ['Aya Bouchiha', 'John Doe'] admins.insert(0, 'Simon Bihao') print(admins) # ['Simon Bihao', 'Aya Bouchiha', 'John Doe']  admins.insert(2, 'Salma Nouhary') print(admins) # ['Simon Bihao', 'Aya Bouchiha', 'Salma Nouhary', 'John Doe']
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pop()

pop(index = -1): delete the elements that exist in the given index, by default the index is the -1 which is the index of the last element. In addition, it returns the deleted element.

admins = ['Aya Bouchiha', 'John Doe'] old_admin = admins.pop() print(old_admin) # John Doe print(admins) # ['Aya Bouchiha']  tasks = ['eat fruits', 'go to gym', 'drink water'] completed_task = tasks.pop(1) print(completed_task) # go to gym print(tasks) # ['eat fruits', 'drink water']
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remove()

remove(value): deletes the first item that matches the given value.

tasks = ['eat fruits', 'go to gym', 'drink water'] tasks.remove('eat fruits') print(tasks.remove('drink water')) # None print(tasks) # ['go to gym'] tasks.remove('something else') # error
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clear()

clear(): used to remove all list's items.

tasks = ['eat fruits', 'go to gym', 'drink water'] print(len(tasks)) # 3  tasks.clear() print(tasks) # [] print(len(tasks)) # 0
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copy()

copy(): this list method is used to return a copy of the specified list.

today_tasks = ['eat fruits', 'go to gym', 'drink water'] tomorrow_tasks = today_tasks.copy() print(tomorrow_tasks) # ['eat fruits', 'go to gym', 'drink water']  today_tasks.clear() print(today_tasks) # []  print(tomorrow_tasks) # ['eat fruits', 'go to gym', 'drink water']
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index()

index(value): returns the index of the first item that matched the given value.

today_tasks = ['eat fruits', 'go to gym', 'drink water'] print(today_tasks.index('eat fruits')) # 0 print(today_tasks.index('drink water')) # 2 print(today_tasks.index('buy a mouse')) # error
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count()

count(value): returns the number of repeated items that match the specified value in a list.

product_prices = [12, 227, 0, 54, 0, 20] free_products_number = product_prices.count(0) print(free_products_number) # 2 print(product_prices.count(224578)) # 0
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extend()

extend(iterable): helps you to insert an iterable(list, set,...) at the end of the specified list.

all_users = ['Yasm', 'Nopay', 'Houssam'] facebook_users = {'Aya', 'Simon'} instagram_users = ('Ayman', 'Soha') all_users.extend(facebook_users) all_users.extend(instagram_users) # ['Yasm', 'Nopay', 'Houssam', 'Simon', 'Aya', 'Ayman', 'Soha'] print(all_users)
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reverse()

reverse(): reverse the order of the specified list

marks = [15, 45, 51, 70] marks.reverse() print(marks) # [70, 51, 45, 15]
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sort()

sort(reverse = False, key(optional)): sort the list's items, if the reverse parameter was True, the items will be sorted in descending order.

the key parameter is used to specify a function that will specify the sorting criteria.

Example:1

marks = [7, 62, 71, 56, 24] marks.sort() print(marks) # [7, 24, 56, 62, 71]  marks.sort(reverse=True) print(marks) # [71, 62, 56, 24, 7]
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Example:2

def get_marks(student: dict): return student.get('marks') students = [ { "name": "Aya Bouchiha", "email": "developer.aya.b@gmail.com", "marks": 92 }, { "name": "John Doe", "email": "john.doe@gmail.com", "marks": 95 }, { "name": "Ryan Hosm", "email": "ryan.hosm@gmail.com", "marks": 80 } ] students.sort(key=get_marks) print(students) # [{'name': 'Ryan Hosm', 'email': 'ryan.hosm@gmail.com', 'marks': 80}, {'name': 'Aya Bouchiha', 'email': 'developer.aya.b@gmail.com', 'marks': 92}, {'name': 'John Doe', 'email': 'john.doe@gmail.com', 'marks': 95}]
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Example3 (using lambda)

products = [ { "name" : "laptop", "price": 500 }, { "name" : "phone", "price": 150 }, { "name" : "mouse", "price": 16 }, { "name": "keyboard", "price": 24 } ] products.sort(reverse=True, key=lambda product: product.get("price")) print(products) highest_price = products[0].get('price') print(f'highest price is: {highest_price}')
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Output:

[{'name': 'laptop', 'price': 500}, {'name': 'phone', 'price': 150}, {'name': 'keyboard', 'price': 24}, {'name': 'mouse', 'price': 16}] highest price is: 500
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Summary

  • append(value): inserts an element at the end of the list.

  • insert(index, value): adds a new element at a given index.

  • pop(index = -1): deletes the element that exist in the given index.

  • remove(value): deletes the first item that match the given value.

  • clear(): removes all list's items.

  • copy(): returns a copy of the specified list.

  • index(value): returns the index of the first item that matched the given value.

  • count(value): returns the number of repeated items that match the specified value in a list.

  • extend(iterable): inserts an iterable at the end of the specified list.

  • reverse(): reverses the order of the specified list.

  • sort(reverse = False, key(optional)): sorts the list's items.

References & useful Resources

Suggested posts

To Contact Me:

email:developer.aya.b@gmail.com
telegram: Aya Bouchiha

Hope you enjoyed reading this post :)

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