Help me in solving PYTH97 problem

My issue

can any one explain me this

Learning course: Learn Python
Problem Link: CodeChef: Practical coding for everyone

The loop will run until a!=b.
Initially we have a=4 and b=1;
inside loop we will print b and increment the value of b.
now first we print b which is 1 and increments its value , now b becomes 2.
now we check the condition.
still a!=b.
then we again print b and increments its value.
so at the end it will print 1,2,3 and when it becomes 4 which is equals to a it will breaks the loop.