# 1501.py

def f(x,a): b=a; b.append(x); return b

a=[1,2]

print f(4,a) # [1, 2, 4]
print a # [1, 2, 4]

b=f(5,a)
print b # [1, 2, 4, 5]
print a # [1, 2, 4, 5]