Are Python Strings Truly Immutable?

Understanding Immutability in Python Strings

Often regarded as immutable, Python strings have left many questioning why appending a string to another using the " " operator appears to modify the original string. Let's delve into this phenomenon.

Consider the following code:

<code class="python">a = "Dog"
b = "eats"
c = "treats"

print(a, b, c)  # Output: Dog eats treats

print(a + " " + b + " " + c)  # Output: Dog eats treats

print(a)  # Still Output: Dog

a = a + " " + b + " " + c
print(a)  # Output: Dog eats treats</code>

Upon assigning "Dog" to the variable "a," you may assume that the string "Dog" is immutable. However, when you append string literals using the " " operator, it creates a new string object with the combined content. In this case, a new string "Dog eats treats" is created, and the variable "a" is reassigned to point to this new string.

Therefore, the immutability of Python strings manifests in the fact that the original string object, in this case "Dog," remains unchanged. The variables, however, can be assigned to point at different string objects, giving the illusion of string mutation.

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