Compare two string and replace letters

Question

If I want to write a function mask(a, b) that takes two strings, a and b, and change the letters to * in a in the order they appear in b, returned in a new string.

For example if s1="How are you doing today" and s2="hardod" than the new string/updated s1 string should be "*ow **e you **ing to*ay".

Is there any way to do this?

def mask(a,b):
    for ch in s2:
    
         s1 = s1.replace(ch, '*', 1)
    return s1

print(mask("How are you doing today", "hardod"))

Then I get the output H*ll*, *ow **e you Anders? which is wrong as they should be replaced in turn, ie the first letter in b should replace the same letter in a on the first index it appears on and no more, then b should continue to the second letter ib and replace the same letter ia on the first index on which it appears and no more etc.

hello, please show us your attempt. At leat, you can walk on a string with a for loop and compare each letter in s1 to s2 then it is the same , replace letter by '*' — DonKnacki, Apr 21 '21 at 11:13
here is a question that can help you- https://stackoverflow.com/questions/3411771/best-way-to-replace-multiple-characters-in-a-string — Prathamesh, Apr 21 '21 at 11:16
@user15415514 : good. Two problems : you should not use s1 and s2 in your function but a and b . About the first letter, as said by @vikash kumar, if you want to not take care about case, you can apply `lower()` to your sting — DonKnacki, Apr 21 '21 at 11:25

score 2 · Accepted Answer · answered Apr 21 '21 at 11:22

2

I would have done something like this :

def mask(a, b):
    start_index = 0
    for c in b:
        for i in range(start_index, len(a)):
            if c == a[i]:
                a = "".join((a[:i], "*", a[i+1:]))
                start_index = i+1
                break
    return a

Your choice to make it case sensitive or not.

answered Apr 21 '21 at 11:22

tronconux

36
2

And if I want to make in insensitive, where do I put `.lower()`? I tried with `if c.lower() == a[I].lower()` but with no success. – user15415514 Apr 21 '21 at 11:41
What you did works for me. But you could just set a and b to lowercase at the start of the function. – tronconux Apr 21 '21 at 13:28

score 0 · Answer 2 · answered Apr 21 '21 at 11:38

def replace(s, position, character):
    return s[:position] + character + s[position+1:]

def mask(a,b):
    indexb=0
    for indexa in range(0,len(a)):
         ch=a[indexa]
         if (ch.lower()==b[indexb]):
            a=replace(a,indexa,'*')
            indexb=indexb+1
            if (indexb==len(b)):
                indexb=0
    return a

print(mask("How are you doing today", "hardod"))

gives

*ow **e you **ing to*ay

Compare two string and replace letters

2 Answers2