How to replace the right letters in a string python

Question

The assignment is:

Your task is correcting the errors in the digitized text. You only have to handle the following mistakes:

S is misinterpreted as 5
O is misinterpreted as 0
I is misinterpreted as 1

My code:

def correct(string):
    for i in string:
        if '5' in string:
           string = string.replace('5','S') 
        elif '0' in string:
          string = string.replace('0','O')
        elif '1' in string:
            string = string.replace('1','I')
    return string

I know this solution will not work for a word like:

Test.assert_equals(correct("51NGAP0RE"),"SINGAPORE");

Does anyone have tips on how to make this a more general function that will work for every word?

Why do you have a for loop, and the if in checks? Just doing the replacements would work better. — internet_user
– internet_user, Commented Apr 13, 2018 at 15:48
On a small number of replacements, @internet_user is correct. See also string.translate for more flexibilty — Reid Ballard
– Reid Ballard, Commented Apr 13, 2018 at 15:51
Are you sure your code doesn't work? It's not as efficient as it could be, but it should still give the correct answer. — Barmar
– Barmar, Commented Apr 13, 2018 at 15:55
Possible duplicate of Multiple character replace with Python — Keyur Potdar
– Keyur Potdar, Commented Apr 13, 2018 at 16:03
Don't name your variable string as it conflicts with the string library- if you're using python2, it would make a difference for the solution given by chrisz — pault
– pault, Commented Apr 13, 2018 at 16:07

Rakesh · Accepted Answer · 2018-04-13 15:51:25Z

5

You can use str.replace directly.

def correct(string):
    return string.replace('5','S').replace('0','O').replace('1','I')

answered Apr 13, 2018 at 15:51

Rakesh

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Comments

user3483203 · Accepted Answer · 2018-04-13 19:21:34Z

5

Why don't you make use of str.maketrans and str.translate:

>>> "51NGAP0RE".translate(str.maketrans('501', 'SOI'))
'SINGAPORE'

Wrapped in a function:

def correct(s):
    return s.translate(str.maketrans('501', 'SOI'))

edited Apr 13, 2018 at 19:21

answered Apr 13, 2018 at 15:53

user3483203

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5 Comments

pault Over a year ago

In python2, this is in the string library. A great reason not to use string as a variable name!

Steve Over a year ago

Thanks for the answer! However it needs to work for every word :)

Olivier Melançon Over a year ago

@DaphneCornelisse You did not understand the answer. This works for every word, not only 501. This is just the way the maketrans function works.

Steve Over a year ago

@OlivierMelançon my bad! I just meant that it had to be a function.

Olivier Melançon Over a year ago

Well then just put that line into a function, it really isn't hard. Plus, this is the best way to go with the kind of problem you are trying to solve. def correct(s): return s.translate(str.maketrans('501', 'SOI'))

Barmar · Accepted Answer · 2018-04-13 15:51:26Z

2

Don't use elif, since that only does a test if the previous one failed. Change them all to ordinary if and the code will work correctly.

But as mentioned in the comments, there's no need for any of the tests. If the letter isn't in the string, replace() will just return the original string, so there's no harm.

string = string.replace('5', 'S').replace('0', 'O').replace('1', 'I')

answered Apr 13, 2018 at 15:51

Barmar

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3 Comments

pault Over a year ago

My initial thought too but OP is iterating over each character in the string, so the elif/if shouldn't make a difference.

Barmar Over a year ago

Good point. If the string is at least 3 characters long it should perform all the replacements.

Barmar Over a year ago

And if it's shorter, it can't need all the replacements.

pault · Accepted Answer · 2018-04-13 16:04:52Z

2

Here's another method using list comprehension:

def correct(str_, replacements = {'5': 'S', '0': 'O', '1': 'I'}):
    return "".join(replacements.get(c, c) for c in str_)
print(correct("51NGAP0RE"))
#'SINGAPORE'

edited Apr 13, 2018 at 16:04

answered Apr 13, 2018 at 15:59

pault

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