In Python, strings are immutable, meaning that once a string is created, it cannot be changed. Let's break this down with some simple examples.

What Does Immutable Mean?

When we say that strings are immutable, it means:

• You cannot change the characters in a string directly.
• If you want to change a string, you have to create a new string.

 

Example 1: Trying to Change a Character

Let's say we have a string:

greeting = "Hello" greeting[0] = "Y" print(greeting[0])

If we try to change the first character 'H' to 'Y', it will give an error because strings are immutable:

>>> TypeError: 'str' object does not support item assignment

 

Example 2: Creating a New String

Instead of changing a string directly, we create a new string. For example, if we want to change "Hello" to "Yello", we can do this:

greeting = "Hello" new_greeting = "Y" + greeting[1:] print(new_greeting)

This code does the following:

1. Takes the original string "Hello".
2. Creates a new string "Yello" by combining "Y" with the substring "ello" (everything except the first character).
3. Prints "Yello".

 

Example 3: Reassigning a Variable

If we reassign a string variable, we are not changing the original string; we are just making the variable reference a new string:

message = "Good morning" message = "Good evening" print(message) #Output: "Good evening"

Here, we change message from "Good morning" to "Good evening". The original string "Good morning" remains unchanged in memory.

Example 4: Using String Methods

String methods like upper(), lower(), replace(), etc., do not change the original string but return a new string:

text = "hello world" new_text = text.upper() print(new_text) #Output: "HELLO WORLD" print(text) #Output: "hello world"

This code:

1. Converts "hello world" to "HELLO WORLD" using the upper() method.
2. Stores the result in new_text.

However, the original text variable is still "hello world".

In Python:

• Strings cannot be changed after they are created.
• To modify a string, you need to create a new string.
• String methods return new strings and do not alter the original.