Why Don't Python String Methods Modify the Original String?

Why String Methods Don't Modify Strings in Python

Python strings are immutable, which means they cannot be directly altered. This can be confusing when using string methods that appear to change the content of a string, such as .replace or .strip.

Consider the following example:

After executing this code, the value of X remains "hello world" instead of the expected "goodbye world". This is because .replace does not modify the original string, but instead returns a new string with the replacements applied. To actually change the value of X, you must assign the output of .replace back to X:

This behavior applies to all Python string methods that modify the string's content, including:

• .replace
• .strip
• .translate
• .lower/.upper
• .join

To use the changes made by these methods, you must always remember to assign their output to the original string or a new variable.

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