why did one value change but the second value did not?

Question

a = [ 1, 2 ]
b = a
a.append(3)
print(b) # shows [ 1 2 3 ] which means b changed

c = 4
d = c
c = 8
print(d) # shows 4 which means d did not change

Why

Answer 1

The answer provided by @DeepSpace is a good explanation.

If you want to check if two variables are pointing to the same memory location you can use is operator and to print them use id.

>>> a=[1,2]
>>> b=a
>>> a is b
True
>>> id(a),id(b)
(2865413182600, 2865413182600)
>>> a.append(2)
>>> a,b,id(a),id(b)
([1,2,2],[1,2,2],2865413182600, 2865413182600)
>>> a=[1,2]
>>> b=[1,2]
>>> a is b
False