Python Lists: Loop Lists

Looping Through Lists

Iterating Over List Items

One of the most common ways to iterate over a list in Python is by using a for loop. This method allows you to access each item in the list sequentially.

Example

To print each item in a list, use a for loop as follows:

my_list = ["The Great Gatsby", "1984", "To Kill a Mockingbird"]
for item in my_list:
    print(item)

This will output:

The Great Gatsby
1984
To Kill a Mockingbird

Iterating Using Index Numbers

You can also loop through a list by referring to the index numbers of its elements. Utilize the range() and len() functions to generate a sequence of indices.

Example

Print each item by accessing its index in the list:

my_list = ["The Great Gatsby", "1984", "To Kill a Mockingbird"]
for i in range(len(my_list)):
    print(my_list[i])

The range(len(my_list)) function generates indices [0, 1, 2], which correspond to the list items.

Looping with a While Loop

A while loop can also be used to iterate through a list. Begin by determining the length of the list with len() and start at index 0. Continue looping until all indices have been processed.

Example

Use a while loop to print each item in the list:

my_list = ["The Great Gatsby", "1984", "To Kill a Mockingbird"]
i = 0
while i < len(my_list):
    print(my_list[i])
    i += 1

In this case, the loop continues as long as i is less than the length of the list, incrementing i with each iteration.

Looping with List Comprehension

List comprehension provides a concise way to loop through lists. This method is particularly useful for applying an operation to each item in the list in a single line of code.

Example

Here’s how you can use list comprehension to print all items in the list:

my_list = ["The Great Gatsby", "1984", "To Kill a Mockingbird"]
[print(item) for item in my_list]

This one-liner achieves the same result as the previous examples, but with more compact syntax.

Exploring different looping techniques helps you efficiently process list elements in Python, enhancing your coding versatility.