Using replace() function in Python to replace vowels in a string

Question

I'm trying to create a function that accepts a string and replaces the vowels with other characters.

I've written some code, but when I run it in IDLE the output is 'None', but I'm expecting it to be '44 33 !! ooo000 ||||'

I have the below:

def vowel_swapper(string):
    for char in string:
        if char in 'aeiouAEIOU':
            char.replace('a', '4').replace('A', '4').replace('e', '3').replace('E', '3')\
            .replace('i', '!').replace('I', '!').replace('o', 'ooo').replace('O', '000').replace('u', '|_|').replace('U', '|_|')

print(vowel_swapper("aA eE iI oO uU"))

Where have I gone wrong here?

Edit: Thanks for all of the responses. I will also take on the advice about using a dictionary and look into it.

Answer 1

In python, .replace is not a in place modification. It returns the result of said modification rather than doing an in place modification.

For what you want to achieve, you cannot do it while looping through the string and possibly assigning each changed char to the string. Python strings are immutable.

Instead, you should do-

def vowel_swapper(s: str):
    return s.replace('a', '4').replace('A', '4').replace('e', '3').replace('E', '3').replace('i', '!').replace('I', '!').replace('o', 'ooo').replace('O', '000').replace('u', '|_|').replace('U', '|_|')

Which will replace all the characters you want to replace at once and return the result.

Output-

44 33 !! ooo000 |_||_|

A more elegant approach however, would be to use a dict.

def vowel_swapper(s: str):
    replacements = {'a': '4', 'A': '4', 'e': '3', 'E': '3', 'i': '!', 'I':  '!', 'o': 'ooo', 'O': '000', 'u': '|_|', 'U': '|_|'}
    return "".join([replacements.get(c, c) for c in s])

Output-

44 33 !! ooo000 |_||_|

Here, we're using .get (with a default value) to efficiently and pythonically, replace and map each character in given string

Answer 2

You are looping through the string and not updating the value of the characters in the string with the replace method.

You can use:

def vowel_swapper(string):
     return string.replace('a', '4').replace('A', '4').replace('e', '3').replace('E', '3').replace('i', '!').replace('I', '!').replace('o', 'ooo').replace('O', '000').replace('u', '|_|').replace('U', '|_|')

vowel_swapper("aA eE iI oO uU")

May I suggest a another way to approach the problem that uses dictionary instead of using replace method multiple times?

string= "aA eE iI oO uU xx"
swap_dic= {'a':'4', 'e':'3','i':'!','o':'000','u':'|_|' }

string= string.lower()

for char in string:
    if char in swap_dic.keys():
        string= string.replace(char,swap_dic[char])
    
print(string)

Answer 3

you don't need to check every character whether they are a vowel or not while using replace, as str.replace return the replace new string with all the replace character with new one

def vowel_swapper(string):

    res = string.replace('a', '4').replace('A', '4').replace('e', '3').replace('E', '3')\
            .replace('i', '!').replace('I', '!').replace('o', 'ooo').replace('O', '000').replace('u', '|_|').replace('U', '|_|')

    return res
print(vowel_swapper("aA eE iI oO uU"))

output

44 33 !! ooo000 |_||_|

Answer 4

The replace method works on entire strings, and returns a new string.

You can save time by converting your string to lowercase, almost halving the methods called.

def vowel_swapper(string):
    return string.replace('o', 'ooo').replace('O', '000').lower().replace('a', '4').replace('e', '3').replace('u', '|_|')

Answer 5

As an alternative to doing replace().replace().replace()... you can use str.maketrans() on a dict() of replacement characters then run translate() on the string:

def vowel_swapper(string):
    table = str.maketrans({'a': '4', 'A': '4',
                           'e': '3', 'E': '3',
                           'i': '!', 'I': '!',
                           'o': 'ooo', 'O': '000',
                           'u': '|_|', 'U': '|_|',
                           }
                          )

    return string.translate(table)


print(vowel_swapper("aA eE iI oO uU"))

Output:

44 33 !! ooo000 |_||_|

Answer 6

def vowel_swapper(stringer):
    new_str = ""
    for char in stringer:
        char = char.replace("A", "4")       # 
These replace the characters
        char = char.replace("E", "3")       # 
Char.replace returns a value rather than resets 
the value of the string it is used on 
        char = char.replace("I", "!")
        char = char.replace("O", "000")
        char = char.replace("U", "|_|")
        char = char.replace("a", "4")
        char = char.replace("e", "3")
        char = char.replace("i", "!")
        char = char.replace("o", "ooo")
        char = char.replace("u", "|_|")

        print(char)
        new_str = new_str + char        # 
creating and building a new string to return 
    return new_str
    
print(vowel_swapper('aA eE iI oO uU'))

when using char.replace() remember it is a method so you get a value out of it.

also your function did not return a value.

:)

Answer 7

Use the letters needed to be removed from the string in dict (we can access the dict in O(1) time complexity)

popouts = {'a': '4', 'A': '4', 'e': '3', 'E': '3', 'i': '!', 'I':  '!', 'o': 'ooo', 'O': '000', 'u': '|_|', 'U': '|_|'}

our input string for example:

sst="fpooabraabdbuuososso"

splited_str=(" ".join(sst)).split()


for j in range(len(splited_str)):
  if splited_str[j] in popouts:
    splited_str[j]=(popouts[splited_str[j]])

final_string="".join(splited_str)

Answer 8

def rep_vowels(vs):
    for i in vs:
        if i in "aeiouAEIOU":
            return vs.replace("a", "*").replace("A", "*").replace("e", "*").replace("E", "*").replace("I", "*").replace("i","*").replace("o","*").replace("O", "*").replace("u", "*").replace("U", "*")

print(rep_vowels("COMPUTER"))  

I've replaced it with star(shift+8)