Are python variables pointers? or else what are they?

We call them references. They work like this

i = 5     # create int(5) instance, bind it to i
j = i     # bind j to the same int as i
j = 3     # create int(3) instance, bind it to j
print i   # i still bound to the int(5), j bound to the int(3)

Small ints are interned, but that isn't important to this explanation

i = [1,2,3]   # create the list instance, and bind it to i
j = i         # bind j to the same list as i
i[0] = 5      # change the first item of i
print j       # j is still bound to the same list as i

Variables are not pointers. When you assign to a variable you are binding the name to an object. From that point onwards you can refer to the object by using the name, until that name is rebound.

In your first example the name i is bound to the value 5. Binding different values to the name j does not have any effect on i, so when you later print the value of i the value is still 5.

In your second example you bind both i and j to the same list object. When you modify the contents of the list, you can see the change regardless of which name you use to refer to the list.

Note that it would be incorrect if you said "both lists have changed". There is only one list but it has two names (i and j) that refer to it.

Related documentation

• Execution Model - Naming and Binding