List vs. int assignment - “Every variable is a pointer”

Question

I know it\'s a very basic question, but I need help understanding this short concept.

I\'m studying Python, and the book says \"Every variable in Python is a pointer to

Answer 1

Your first example can be explained as follows:

x=[1,2,3]  # The name x is assigned to the list object [1,2,3]
y=x        # The name y is assigned to the same list object referenced by x
x[1]=3     # This *modifies* the list object referenced by both x and y
print y    # The modified list object is printed

The second example however only reassigns the name x to a different integer object:

x=5      # The name x is assigned to the integer object 5
y=x      # The name y is assigned to the same integer object referenced by x
x=7      # The name x is *reassigned* to the new integer object 7
print y  # This prints 5 because the value of y was never changed

Here is a reference on assignment in Python.