Why Don't Python's String Methods Like `.replace()` Modify the Original String?

Why String Methods Like .replace() Don't Alter Strings Directly in Python

When attempting to modify a string using methods like .replace() or .strip() in Python, you may find that the original string remains unchanged. This behavior stems from the immutability of strings in the language.

Immutable objects, as the name suggests, cannot be modified in place. Instead, calling a method on an immutable object returns a new object with the desired changes. For example, in Python:

X = "hello world"
new_string = X.replace("hello", "goodbye")

In the code above, .replace() returns a new string with the replacement made. However, the original variable X still holds the unmodified string "hello world." To update the value of X, you must assign the result of the method call:

X = X.replace("hello", "goodbye")

This principle applies to all string methods in Python that alter the content of a string, including:

• .replace()
• .strip()
• .translate()
• .lower()
• .upper()
• .join()
• .capitalize()
• .casefold()

Therefore, it's essential to assign the output of these methods to a new variable or the same variable if you wish to retain the modified string.

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