How to delete consonants from a string in Python?

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

Using Loop

In this approach, we are going to declare the variable assignment with vowels in both upper and lower case and then looping through each character in the string. If the character is vowel or a non-alphabet character we will retrieve them and add to result.

Example

Let's look at the following example, where we are going to remove the consonants from the string "TutorialsPoint".

def demo(a):
    x = 'aeiouAEIOU'
    result = ''
    for char in a:
        if char in x or not char.isalpha():
            result += char
    return result
print(demo("TutorialsPoint"))

The output of the above program is as follows -

uoiaoi

Using List Comprehension

The second approach is by using the Python list comprehension, Where it is used to filter the characters and selects only the vowels and non-alphabetic characters. Then we will combine all those characters to form the single string using the join() method.

Example

In the following example, we are going to use the list comprehension and removing the consonants from the string.

def demo(text):
    x = 'aeiouAEIOU'
    return ''.join([char for char in text if char in x or not char.isalpha()])
print(demo("Welcome to TP."))

The following is the output of the above program -

eoe o .

Using Regular Expression

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

Example

Consider the following example, where we are going to remove the consonants from the string using the regular expression.

import re
def demo(text):
    return re.sub(r'(?i)[b-df-hj-np-tv-z]', '', text)
print(demo("Welcome"))

The following is the output of the above program -

eoe