I thought that strings are immutable?

Question

I've always thought that strings and tuples are immutable in Python. But now I've been confused with this function that I wrote (down below). When it's executed, I get a mutable string indeed. Am I missing something here?

def example():
    string = "/*Jon is @developer & musician"
    for char in string:
        if not char.isalpha():
            string = string.replace(char, '#')
    return(string)

Output:

>>> example()
'##Jon#is##developer###musician'
>>>

Thanks in advance for your explanation!

You never mutate a string anywhere in your code. *Where* do you think you mutated a string? — juanpa.arrivillaga, Feb 07 '22 at 18:43
You create a NEW string, but you assign it in the SAME variable — azro, Feb 07 '22 at 18:45
Yup, you're missing something. You've just misunderstood what it means to mutate something. You aren't mutating the original string because you are re-binding it. — Paul M., Feb 07 '22 at 18:45
Mutation means that you can call a method on an object and it changes. You have not done that. You have called a method on an object and gotten a completely new thing! — Ted Klein Bergman, Feb 07 '22 at 18:46

score 0 · Answer 1 · answered Feb 07 '22 at 18:47

0

The string's replace method is not a in-place function. It creates a new string.

If instead you tried to run string[0] = "a" for example, you would have gotten an error.

answered Feb 07 '22 at 18:47

Daniel Tomer

96
4

I thought that strings are immutable?

1 Answers1