Lec-22: List Functions In Python 🐍 | Built in Functions Python 🐍

Summary

This tutorial explains various Python list functions, ideal for beginners and those preparing for exams. It covers creating lists, using functions like `len`, `append`, `extend`, `insert`, and `count`, and demonstrates methods to remove, pop, and sort elements. The video also highlights how to find the smallest or largest element using `min` and `max`, as well as the `reverse` function. Special attention is given to handling duplicates, sorting in ascending/descending order, and managing lists with multiple values. The presenter emphasizes the importance of mastering these functions for Python interviews and exams.

Takeaways

• 😀 Lists are an essential data structure in Python and can be created using square brackets or the list() function.
• 😀 You can access list elements using their index, with indexing starting from 0 in Python.
• 😀 The length of a list can be obtained using the built-in `len()` function, which counts the total number of elements.
• 😀 The `append()` method adds a single element to the end of the list.
• 😀 Use `insert()` to add an element at a specific index in the list.
• 😀 The `extend()` method allows you to add multiple elements at once to the list.
• 😀 The `remove()` method removes the first occurrence of a specified element from the list.
• 😀 The `pop()` method removes an element at a given index and returns it, enabling element manipulation during list operations.
• 😀 You can sort a list in ascending or descending order using the `sort()` method, with the `reverse=True` argument for descending order.
• 😀 To reverse a list in place, use the `reverse()` method. Alternatively, `sorted()` returns a sorted copy of the list without modifying the original.
• 😀 The `count()` method counts how many times a specific element appears in the list, helping to track element frequency.

Q & A

What is a Python list and how is it created?

A Python list is a mutable data structure that can hold multiple items. It is created by placing elements inside square brackets, separated by commas, e.g., `my_list = [10, 20, 30, 40]`.

How can you access an element from a list in Python?

Elements in a Python list are accessed using indexing. Indexing starts from 0. For example, `my_list[0]` will return the first element of the list.

What does the `len()` function do when used with a list?

The `len()` function returns the number of elements present in a list. For example, `len(my_list)` will return the total number of items in the list.

How can you add an element to the end of a list in Python?

You can add an element to the end of a list using the `append()` method. For example, `my_list.append(50)` will add 50 to the end of the list.

What is the purpose of the `insert()` method in Python lists?

The `insert()` method allows you to add an element at a specific index in a list. For example, `my_list.insert(2, 25)` inserts 25 at index 2 of the list.

How can you extend a list with another list in Python?

You can extend a list by using the `extend()` method, which adds all elements from another list to the current list. For example, `my_list.extend([60, 70])` will add 60 and 70 to the end of `my_list`.

What is the difference between `remove()` and `pop()` methods in Python?

`remove()` removes the first occurrence of a specified value from the list, while `pop()` removes and returns an element at a specific index or the last element by default.

How does the `sort()` method work in Python?

The `sort()` method sorts the elements of a list in ascending order by default. For example, `my_list.sort()` will reorder the list in increasing order.

What is the difference between the `sort()` method and the `sorted()` function?

The `sort()` method sorts a list in place, meaning it modifies the original list, while the `sorted()` function returns a new list that is sorted, leaving the original list unchanged.

How can you count the occurrences of an element in a list?

You can count the occurrences of an element using the `count()` method. For example, `my_list.count(20)` will return the number of times 20 appears in `my_list`.