CODEWITHSUNDEEP
pythonloopsreplaceiteration
user15261256
user15261256

Reputation: 11

How do I stop this from exiting after the first iteration?

I'm trying to return a statement that replaces given old characters with new characters, but the loop keeps exiting after the first iteration.

def test(s, old_ch, new_ch): 
    """returns the given input and replaces an old character with a new character""" 
    newstring = "" 
    for ch in s: 
        while (ch == old_ch): 
            newstring += new_ch  
            break
        while (ch != old_ch):
            newstring += ch 
            break 
        return newstring

I know that there are already defined replace functions in python, but this is the way I've been told to do it. (same with the for ch in s bits)

Upvotes: 1

Views: 1319

Answers (3)

arun n a
arun n a

Reputation: 906

Try this, so that you will get a better understanding of the iteration.

def test(s, old_ch, new_ch): 
    newstring = "" 
    for ch in s:
        print(f"ch is {ch}")
        if (ch == old_ch):
            print(f"if condition is True for ch {ch} and old_ch {old_ch}")
            newstring += new_ch  
        else:
            print(f"elif condition is True for ch {ch} and old_ch {old_ch}")
            newstring += ch
    print(newstring)
    return newstring

call this function

test("New to Python", "t", "y")

Output is

ch is N
elif condition is True for ch N and old_ch t
ch is e
elif condition is True for ch e and old_ch t
ch is w
elif condition is True for ch w and old_ch t
ch is  
elif condition is True for ch   and old_ch t
ch is t
if condition is True for ch t and old_ch t
ch is o
elif condition is True for ch o and old_ch t
ch is  
elif condition is True for ch   and old_ch t
ch is P
elif condition is True for ch P and old_ch t
ch is y
elif condition is True for ch y and old_ch t
ch is t
if condition is True for ch t and old_ch t
ch is h
elif condition is True for ch h and old_ch t
ch is o
elif condition is True for ch o and old_ch t
ch is n
elif condition is True for ch n and old_ch t

Upvotes: 0

Amit Karnam
Amit Karnam

Reputation: 3

for ch in s statement is used to loop over every character of the string. Hence the while loop inside the for loop is not required.

def test(s, old_ch, new_ch): 
    """returns the given input and replaces an old character with a new character""" 
    newstring = "" 
    for ch in s: 
        if(ch == old_ch): 
            newstring = newstring+new_ch  
            
        if(ch != old_ch):
            newstring = newstring + ch 
            
    return newstring

This code does the intended work you want to achieve.

Upvotes: 0

M-Chen-3
M-Chen-3

Reputation: 2054

There are two things you need to change.

  1. Instead of using a while-loop and breaking, just use an if-statement. Your code will still work the same way, but it'll be much more readable.

  2. Move the return statement outside of the for-loop, i.e. unindent it. This way newstring won't be returned until the entire for-loop has been executed, which is the desired behavior.

The full corrected code is below:

def test(s, old_ch, new_ch): 
    """returns the given input and replaces an old character with a new character""" 
    newstring = "" 
    for ch in s: 
        if (ch == old_ch): 
            newstring += new_ch  
        else:
            newstring += ch 
    return newstring

print(test("Megalovania", "a", "o"))
# Prints Megolovonio

Upvotes: 1

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