Python Program to Iterate Over a List

In this article, we will show how to write a Python program to iterate or traverse over a list of elements with examples. There are multiple options to iterate over the elements or items in a list, including the for loop, range, while loop, enumerate, list comprehension, lambda, map, and chain function. You can use any of the below methods based on your requirements.

Python Program to Iterate Over a List Using a For Loop

The for loop is the most popular and best approach to iterate over a list of elements. In the program below, we have declared an integer list of six elements. Next, the door loop will iterate over num list and print the values in it. Here, val is the actual value of the num list element.

num = [5, 10, 15, 20, 25, 30]

for val in num:
    print(val)

Using a for loop with range

You can also use the range() function along with the for loop to iterate the list index positions. From the example below, the len() will find and return the total items. Next, the range() function accepts start, stop, and step args. It means the for loop will iterate the list index from 0 to n (len() -1). We have used the index position to access the list item. Refer to the Python For loop article and the Python range function.

num = [10, 20, 30, 40, 50]

for i in range(len(num)):
    print(num[i])

Iterate over list elements using enumerate

The enumerate function is very helpful in iterating the list items and accessing the index position along with the actual element. In the below. Program, i is the index position, and val is the list element present at that position.

num = [10, 20, 30, 40, 50]

for i, val in enumerate(num):
    print(i, "Position =", val)

0 Position = 10
1 Position = 20
2 Position = 30
3 Position = 40
4 Position = 50

Program to iterate over multiple lists using the zip function

If the task is to iterate over multiple lists at the same time, we use the zip() function to hold them together. The for loop will iterate over items from the two lists at each index. Refer to the Python zip.

fruits = ['apple', 'banana', 'orange', 'strawberry']
n = [20, 50, 10, 400]
for fruit, stock in zip(fruits, n):
    print(f"{fruit}s = {stock}")

apples = 20
bananas = 50
oranges = 10
strawberrys = 400

Using List Comprehension

On par with the first example, list comprehension is the best approach to iterate over the elements in a list. It internally uses the for loop to iterate the list item, but it provides the shortest and most readable syntax. Refer to the Python list comprehension.

num = [10, 20, 30, 40, 50]

[print(val) for val in num]

Python Program to Iterate Over a List Using lambda and map

Here, the Python lambda a:a means it accepts every element in a Python list iterable and returns the same. The list function converts the Python map object.

num = [10, 20, 30, 40, 50]

res = list(map(lambda a:a, num))

print(res)

[10, 20, 30, 40, 50]

Using itertools

The itertools module has the chain function that can be helpful to traverse over list items. If you use the cycle() function (itertools.cycle(num)), it will enter the infinity loop and print the below five records an infinite number of times.

import itertools

num = [10, 20, 90, 40, 50]

for val in itertools.chain(num):
    print(val)

Python Program to Iterate Over a List Using a While Loop

This program uses a while loop instead of a For loop to iterate the integer list item and prints the elements. Don’t forget to increment the i value. For more examples, refer to the Python Basic Programs and also check out the Python while loop.

num = [5, 10, 15, 20, 25, 30]

i = 0
while i < len(num):
    print(num[i])
    i = i + 1

Using the NumPy module to iterate over a list

The NumPy array function converts the list to an ndarray. Next, the for loop iterates over it to print the list items.

import numpy as np
fruits = ['apple', 'banana', 'orange', 'strawberry']
for i in np.nditer(np.array(fruits)):
    print(i)

apple
banana
orange
strawberry

The other option is to use the range() function with the Python len method

import numpy as np
fruits = ['apple', 'banana', 'orange', 'strawberry']
for i in range(len(np.array(fruits))):
    print(fruits[i])

apple
banana
orange
strawberry

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