Why doesn't calling a string method (such as .replace or .strip) modify (mutate) the string?
python, string
Solution
This is because strings are immutable in Python.
Which means that `X.replace("hello","goodbye")` returns a copy of `X` with replacements made. Because of that you need to replace this line:
X.replace("hello", "goodbye")
with this line:
X = X.replace("hello", "goodbye")
More broadly, this is true for all Python string methods that change a string's content, e.g. `replace`,`strip`,`translate`,`lower`/`upper`,`join`,...
You must assign their output to something if you want to use it and not throw it away, e.g.
X = X.strip(' \t')
X2 = X.translate(...)
Y = X.lower()
Z = X.upper()
A = X.join(':')
B = X.capitalize()
C = X.casefold()
and so on.
Problem
I tried this code to do simple string replacement: ``` X = "hello world" X.replace("hello", "goodbye") ``` Why doesn't `X` change, from `"hello world"` to `"goodbye world"`?