CODEWITHSUNDEEP
stringpython-2.7loops
Jessica
Jessica

Reputation: 135

Replacing every other instance of a letter with a substring

I have a question on my coding. I'm writing a code that with every OTHER instance of the letter "a" in a string, it needs to be replaced by "dragon". So if the string was abadifaa, my code should return "abdragondifadragon."

So far, I have written the code for replacing every instance of "a"

def replace(string1, dragon):


new_string = " "

for letter in string1:

    if letter != "a":

          new_string +=letter

    elif letter == "a':

          new_string += dragon

    return new_string

So I have 2 questions. 1. Is my code correct if the question asked for every instance of "a" to be replaced? 2. How would I change this code to iterate and replace through only every other instance of "a"?

Appreciate the help!

Upvotes: 0

Views: 104

Answers (2)

Eugene
Eugene

Reputation: 1639

First of all, you need to indent your function definition:

def replace(string1, dragon):
   new_string = " "
   for letter in string1:
       if letter != "a":
             new_string +=letter
       elif letter == "a':
             new_string += dragon
       return new_string

Also, it's more readable not to double-space lines.

Secondly, dragon is a variable, not a string. Here I default dragon to the string 'dragon':

def replace(string1, dragon='dragon'):
   new_string = " "
   for letter in string1:
       if letter != "a":
             new_string +=letter
       elif letter == "a':
             new_string += dragon
       return new_string

However it is better to rename the variable:

def replace(string1, replace_word='dragon'):
   new_string = " "
   for letter in string1:
       if letter != "a":
             new_string +=letter
       elif letter == "a':
             new_string += replace_word
       return new_string

Now, you want to replace every other 'a'. Easy way, and intuitive (there are many other clever ways, but for beginners, this is easiest to understand). Create a counter of a's, and only replace if the modulo when divided by 2 is zero. This means every even number of a_counter, which is every other instance of a.

def replace(string1, replace_word='dragon'):
    a_counter = 0
    new_string = ''
    for letter in string1:
        if letter != 'a':
            new_string += letter
        elif letter == 'a':
            a_counter += 1
            if a_counter%2 == 0:
                new_string += replace_word
            else:
                new_string += letter
    return new_string

print replace('abadifaa', 'dragon')

Also, your quotes are not correct (fixed above, you were mixing ' and ""), and your return is nested too deep (you want to only return once you have iterated over all the letters).

Here is a coderpad to see it in action: https://coderpad.io/KPM3K7PG

(edited a few mistakes from original answer, like appending all letters).

Upvotes: 1

Ehsan Misaghi
Ehsan Misaghi

Reputation: 76

You have forgotten a few quotation marks and your new_string should be empty (you have a space in it now). Other than these, your code changes every instance of "a" to "dragon". I would recommend adding a counter variable into your code, so that every time the counter is an even number, the letter "a" is replaced and every time it is an odd number, it is left as-is.

Upvotes: 0

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