How to shift vowels in input string with Python

Question

I am trying to write a function that would let me shift the individual letters in a string. The string comes from the input.

I'm looking at vowels so "a, e, i, o, u"

I would like the individual letter to be shifted one to the right. i.e the world "me" would become "mi" as i is the next letter after e.

this is what I have so far:

import random
vowels = ("a", "e", "i", "o", "u")

message = input("Enter a string")

new_message = ""

for letter in message:
    if letter not in vowels:
        new_message += letter
    else:
        new_message += random.choice(vowels)
        
print(new_message)

However, this randomizes the changing of the individual vowels, what would be the best way to make it shift to the next letter?

you want to use the next letter right, then why are you using random ? — Sai Sreenivas, Jul 24 '20 at 13:26
See also https://stackoverflow.com/questions/8886947/caesar-cipher-function-in-python which has several interesting variations, some of which will easily accommodate your use case. — tripleee, Jul 27 '20 at 09:43

score 6 · Answer 1 · answered Jul 24 '20 at 13:37

6

If you want to translate the whole string, then I would look at str.translate.

Here is a simple example working with your vowels:

>>> v = "aeiou"
>>> vDict = {v[i]: v[(i+1)%len(v)] for i in range(len(v))}
>>> vDict
{'a': 'e', 'e': 'i', 'i': 'o', 'o': 'u', 'u': 'a'}
>>> "This is a test-string. hope it works!".translate(str.maketrans(vDict))
'Thos os e tist-strong. hupi ot wurks!'

answered Jul 24 '20 at 13:37

Hampus Larsson

3,050
2
14
20

I didn't know you could give a dictionary to `str.maketrans`. Nice! – Chris Charley Jul 25 '20 at 00:39

score 2 · Accepted Answer · answered Jul 24 '20 at 13:39

2

That was true. Using dictionary should fix it

import random
vowels = {"a":"e", "e":"i", "i":"o", "o":"u", "u":"a"}

message = input("Enter a string : ")

new_message = ""

for letter in message:
    if letter not in vowels:
        new_message += letter
    else:
        new_message += vowels[letter]
        
print("Converted text : " + new_message)

output :

Enter a string : hello sir
Converted text : hillu sor

answered Jul 24 '20 at 13:39

Philip Purwoko

407
5
20

2

An alternative: The complete `for` loop could be replaced by `new_message = ''.join(vowels.get(c, c) for c in message)` – Matthias Jul 24 '20 at 15:41

score 1 · Answer 3 · answered Jul 24 '20 at 13:36

vowels = ["a", "e", "i", "o", "u"]

mapper = dict(zip(vowels, vowels[1:] + [vowels[0]])
message = input("Enter a string")

new_message = ""

for letter in message:
    new_message += mapper.get(letter, letter)
        
print(new_message)

However, i would recommend using re library

import re

new_message = re.sub("\S", lambda x: mapper.get(x.group(0), x.group(0)))

Note, in both methods, the character is replaced by itself if no corresponding mapper exists, else with the mapper item

score 0 · Answer 4 · answered Jul 24 '20 at 13:35

0

You can change your method to:

for letter in message:
    if letter not in vowels:
        new_message += letter
    else:
        i = vowels.index(letter)
        i+=1
        new_message += vowels[i]

This way, the function would find the index of the vowel in the vowels array and update it by one to add the next vowel in the new message

answered Jul 24 '20 at 13:35

Kanza Sheikh

65
6

Doesnt account for replacing "u" – vestronge Jul 24 '20 at 13:36

score 0 · Answer 5 · answered Jul 24 '20 at 13:43

Maybe your else could look something like this:

next_vowel_index = vowels.index(letter) + 1
if next_vowel_index >= len(vowels):
    next_vowel_index = 0
new_message += vowels[next_vowel_index]

This code takes the index of the current vowel and increments it by one, unless it is the last vowel in the tuple, in which case it sets the index to zero.

How to shift vowels in input string with Python

5 Answers5