The assignment in Python is different from C/C++, in C/C++, the below code means allocate 4 bytes memory on the stack to store an integer varaible.

int a = 1;

However everything in Python is an object. The below code in Python means create a integer object in memory and label it with a variable called a. You can think of a as a pointer which points to the integer object.

a = 1

What happens when you modify a variable? It depends on the type of the variable. It is worth noting that Python is a strongly typed language. Different from statically typed language, Python is dynamically-typed language. If the type is immutatble, like int, float, string, tuple etc. Changing a variable will create a new object and label it with the variable.

a = 1
a += 1 # create a new integer object with value 2 and label it with variable a

If the type is mutable, changing a variable will change the object it points to. Check the below example.

lst = []
print(id(lst))
lst.append(1)
print(id(lst)) # the output is same as the output of second line