Iterate over a list in Python

Python provides several ways to iterate over list. The simplest and the most common way to iterate over a list is to use a for loop. This method allows us to access each element in the list directly.

Example: Print all elements in the list one by one using for loop.

a = [1, 3, 5, 7, 9]

# On each iteration val
# represents the current item/element
for val in a:
    print(val)

1
3
5
7
9

Let’s see other different ways to iterate over a list in Python.

Using for Loop with range()

We can use the range() method with for loop to traverse the list. This method allow us to access elements by their index, which is useful if we need to know the position of an element or modify the list in place.

a = [1, 3, 5, 7, 9]
 
# Calculate the length of the list
n = len(a)
 
# Iterates over the indices from 0 to n-1 (i.e., 0 to 4)
for i in range(n):
    print(a[i])

1
3
5
7
9

Using while Loop

This method is similar to the above method. Here we are using a while loop to iterate through a list. We first need to find the length of list using len(), then start at index 0 and access each item by its index then incrementing the index by 1 after each iteration.

a = [1, 3, 5, 7, 9]
 
# Start from the first index
i = 0
 
# The loop runs till the last index (i.e., 4)
while i < len(a):
    print(a[i])
    i += 1

1
3
5
7
9

Using enumerate()

We can also use the enumerate() function to iterate through the list. This method provides both the index (i) and the value (val) of each element during the loop.

a = [1, 3, 5, 7, 9]

# Here, i and val reprsents index and value respectively
for i, val in enumerate(a):
    print (i, val)

0 1
1 3
2 5
3 7
4 9

Using List Comprehension

List comprehension is similar to for loop. It provides the shortest syntax for looping through list.

a = [1, 3, 5, 7, 9]
 
# On each iteration val is passed to print function
# And printed in the console.
[print(val) for val in a]

1
3
5
7
9

Note: This method is not a recommended way to iterate through lists as it creates a new list (extra space).

Related Articles:

• Iterate Over a List of Lists in Python
• Iterate Over a Numpy Array
• Iterate over multiple lists simultaneously
• Iterate through list without using the increment variable