When we write a complex program, the flow of logic is very important. At the same time, some good comments or explanations will help other programmers, other users, and even ourselves greatly. For a program that is not well documented, its author might have a hard time understanding it a few months later. We could add comments in many places. For example, at the beginning of the program, we could write the name of the program, objective, input variables, output variables, author or authors of the program, version of the program, and contact information. Some comments could be long, while others could be just a phrase. To satisfy various needs, Python has different types of methods to add comments. When the underlying software compiles the program, those comments could be ignored automatically.

>>>fv=100 # this is comment
>>>fv
100