Lists form an essential part of data structures and algorithms in Python. They play an important role, and ignoring them in your projects is almost impossible.
Due to the large importance of lists, Python provides some built-in functions to perform common list operations. These functions aim to help developers work faster and easier.
1. The len() Function
Use thelen()function to get the number of items inside a list. Here’s an example:
Without thelen()function, you would have to manually calculate length, like in this example which usesa Python for loop:
From this example, it is obvious that thelen()function saves some code. Ensure you use it whenever the need arises.
2. The append() Function
Theappend()function adds a new item to the end of your list. A good use of this is to add an item to your list after your code fulfills a certain condition. Here’s a simple example:
This example uses anif statementto add a certain sentence to the initial list based on the user’s input.
Theappend()function can add only one item at a time to your list. Instead of the append function, you may use an operator instead:
Using the addition operator will ultimately be less efficient because it doesn’t modify your initial list. Instead, it creates a new list in memory and adds a new item to it. Theappend()function modifies your initial list directly.
3. The extend() Function
Theextend()function is a built-in function that adds several items to an existing list at once. It takes in the new items as an argument and modifies your existing list with the argument. Here’s how to use theextend()function:
Theextend()function can only take one argument, so you should add all your items to a list like the code above.
4. The reverse() Function
The reverse function simply rewrites your list in the reverse order. Here’s an example of the reverse function in use:
To reverse a list without using thereverse()function, you would need to slice your list. Here’s an example:
In the above example,my_list[::-1]creates a reversed copy of the original list. This means you’ll have two lists in memory, which is not the best approach if you simply want to reverse the original list.
5. The insert() Function
Theinsert()function modifies a list and adds an item to it like theappend()function. However, theinsert()function allows you to specify the index (position) of your new item in the list. Here’s an example:
From the above code, this is the correct syntax to use theinsert()function:
6. The sort() Function
Thesort()function takes a list of a particular data type and rearranges the elements in ascending order. Here’s an example:
If you use thesort()function on a list with different data types, such as strings and numbers, you will get a TypeError.
7. The count() Function
Thecount()function counts the number of times a specific element occurs in a list and returns the value to you. Here’s how to use it:
Performing such an operation without thecount()function would require you to write more code. Here’s an example:
Thelen()function will return the total number of elements in a list, while thecount()function will return the number of times a specific element occurs in a list.
Using List Functions to Write Better Code
When working with lists in Python, it is important to use the available list functions to write efficient and clean code. They generally save you from writing complex and time-consuming code.
List functions enable you to easily perform common list operations, giving you more time to focus on other parts of your code.
