How to delete consonants from a string in Python?

The consonants are the alphabetic characters that are not vowels (a, e, i, o, u). In Python, string manipulation is a common task. In this article, we will explore how to delete consonants from a string using different approaches, including loops, list comprehensions and regular expressions.

Using Loop

In this approach, we declare a variable containing vowels in both upper and lower case, then loop through each character in the string. If the character is a vowel or a non-alphabet character, we add it to the result ?

Example

Let's look at the following example, where we remove consonants from the string "TutorialsPoint" ?

def remove_consonants(text):
    vowels = 'aeiouAEIOU'
    result = ''
    for char in text:
        if char in vowels or not char.isalpha():
            result += char
    return result

print(remove_consonants("TutorialsPoint"))

The output of the above program is as follows −

uoiaoi

Using List Comprehension

The second approach uses Python list comprehension to filter characters and select only vowels and non-alphabetic characters. We then combine all those characters to form a single string using the join() method ?

Example

In the following example, we use list comprehension to remove consonants from the string ?

def remove_consonants(text):
    vowels = 'aeiouAEIOU'
    return ''.join([char for char in text if char in vowels or not char.isalpha()])

print(remove_consonants("Welcome to TP."))

The following is the output of the above program −

eoe o .

Using Regular Expression

In this approach, we use Python regular expressions. Here we use the regex pattern '(?i)[b-df-hj-np-tv-z]' to match all consonants regardless of case and replace all consonants with empty string using the Python re.sub() method ?

Example

Consider the following example, where we remove consonants from the string using regular expression ?

import re

def remove_consonants(text):
    return re.sub(r'(?i)[b-df-hj-np-tv-z]', '', text)

print(remove_consonants("Welcome"))
print(remove_consonants("Python Programming"))

The following is the output of the above program −

eoe
yo oai

Comparison

Conclusion

Use list comprehension for clean, readable code when removing consonants. Regular expressions are best for complex pattern matching, while loops provide the most straightforward approach for beginners.