Congratulations! In Chapter 3, Calculate This!, you wrote a calculator program. If you followed the instructions and corrected your errors, then you have a program that runs all of the mathematical functions with two numbers. While this is great for a first program, that sort of a limited calculator doesn't give a user much choice. When the user runs the calculator, the program will not end until all five functions have run or until the program ends due to an error.

What if, instead of doing the entire math, we could program our calculator to perform certain operations based on the way the users answer our questions? As programmers, we can use Python to interpret user data and change the way the program operates. In this chapter, you will learn how to use control flows so that our calculator program can make choices and only run the code that the user chooses.

At the end of this chapter, you will have a calculator program that can choose which...