This work 'Definition_of_Prime_Numbers', displays all prime numbers less than a certain input number. This may not be one of the interesting things to do with python but it gets one playing with python and numbers. To appreciate this work, think of how you would define a prime number using python. Try to display some prime numbers. If you have done that, sure a lot of thinking took place. It is the case for this work as well. But is fun thinking and getting the results after all.