Isn't indenting of if and else necessary in python?

Question

In the code given below , the if and else are in different indentation but it still works.
However if I indent the else to match the it's indentation nothing prints out. Can someone say why?

num = int(input("enter a number: "))
for i in range(2, int(num/2)):
 if num % i  == 0:
  print("not prime number")
break
else:
 print("prime number")

Answer 1

This is an extended function of else. If you write it after a loop like this it means:

If the break command is executed do operation 1;

but if that doesn't happen and the loop runs through to the end, then (else) execute operation 2.

Answer 2

Thanks