List assignment in python

Question

num1=[1,2,3,4]
num2=num1
print(num1)
num2[0]=5
print(num1[0])

Above code last line output 5, why?

Answer 1

Array is by default reference type.
If you assign a array to another variable. That variable has the same reference to that array. if you change value of one array others will also change.