Converting all Strings in a List to Integers - Python

We are given a list of strings containing numbers and our task is to convert these strings into integers. For example, if the input list is ["1", "2", "3"] the output should be [1, 2, 3]. Note: If our list contains elements that cannot be converted into integers such as alphabetic characters, strings or special symbols, trying to convert them using int() will raise a ValueError or Invalid Literal Error. Let's discuss various ways to convert all string elements in a list to integers in Python.

Using map()

map() function applies a given function to all elements in an iterable. Here, we use map(int, a) to convert each string in the list to an integer.

a = ['2', '4', '6', '8']

b = list(map(int, a))
print(b)

[2, 4, 6, 8]

Explanation:

• map(int, a) applies the int() function to every item in the list 'a'.
• list(map(int, a)) converts the result of map() into a list.

Using list comprehension

List comprehension provides a more Pythonic and concise way to convert a list of strings to integers as it combines the conversion and iteration into a single line of code.

a = ['2', '4', '6', '8']

b = [int(item) for item in a]
print(b)

[2, 4, 6, 8]

Explanation:

• int(item) converts each string in the list to an integer.
• [int(item) for item in a] this list comprehension goes through each element (item) of 'a', applies int() and collects the results in a new list.

Using a loop

In this approach we iterate over the list using a loop (for loop) and convert each string to an integer using the int() function.

a = ['2', '4', '6', '8']

for i in range(len(a)):
  
    a[i] = int(a[i])

print(a)

[2, 4, 6, 8]

Explanation:

• for i in range(len(a)) iterates over the indices of the list a.
• a[i] = int(a[i]) converts each string at index i to an integer and updates the list in place.

Related Articles:

• Python map() function
• List Comprehension in Python
• Python For Loops
• Convert integer to string in Python
• Convert String to Integers in Python
• Convert number to list of integers in Python
• Integers String to Integer List in Python