CODEWITHSUNDEEP
python
Perceptic
Perceptic

Reputation: 463

Python - Replacing letters in a string?

I am basically writing a simple function in which the user enters a sentence (strng), a letter (letter) and another letter (replace) to replace the first letter with. Here's what I have:

def letter_replace(strng, letter, replace):
    replace = str(replace)
    for char in strng:
        if char == letter.upper() or char == letter.lower():
            strng.replace(char, replace)
            return strng
        else:
            return "Sorry, the letter could not be replaced."

I can't figure out why this won't work. Sorry if it's a completely obvious mistake, I am fairly new to Python. Thanks

Upvotes: 2

Views: 7620

Answers (4)

Joran Beasley
Joran Beasley

Reputation: 113940

use string translate!!!

import string
old_chars = "aeiou"
replace_chars = "!@#$%"
tab = string.maketrans(old_chars,replace_chars)
print "somestring".translate(tab)

oh nevermind... I just read you only want to use one character ...

use string.replace ...

Upvotes: 0

awesoon
awesoon

Reputation: 33651

You could do this using regex:

In [11]: import re

In [12]: def letter_replace(s, l, r):
   ....:     p = re.compile(l, re.IGNORECASE)
   ....:     return p.sub(r, s, 1)
   ....: 

In [13]: letter_replace('AaBbCc', 'a', 'x')
Out[13]: 'xaBbCc'

Upvotes: 0

kindall
kindall

Reputation: 184091

strng.replace(char, replace)

This does the replacement, creating a new string, and then throws away the changed string because you don't assign it to a variable.

Since you're just going to return it anyway, you can simply write:

return strng.replace(char, replace)

Upvotes: 3

Sukrit Kalra
Sukrit Kalra

Reputation: 34493

strings are immutable, you need to assign it to a new variable and return that. replace() returns a new string and does not change it in place.

>>> def letter_replace(strng, letter, replace):
    replace = str(replace)
    for char in strng:
        if char == letter.upper() or char == letter.lower():
            strng = strng.replace(char, replace)
            return strng   # Or just do return strng.replace(char, replace)
        else:
            return "Sorry, the letter could not be replaced."


>>> letter_replace('abc', 'a', 'f')
'fbc'

Upvotes: 6

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