I am trying to write a prime number program in python. But when user inputs 3. My program is not working. Further checking with print statements i found its not going in for loop.
I'm going to assume in your program you have
i is the input. When your user inputs 3, there will be no range since you're going from 3 to 3.
A good way to fix this is at the beginning of the function. Before you get your range, return
[2,3] if the input is 3 (I assume you are doing something similar for 2)