Effective Computation in Physics

Chapter 4. Flow Control and Logic

Flow control is a high-level way of programming a computer to make decisions. These decisions can be simple or complicated, executed once or multiple times. The syntax for the different flow control mechanisms varies, but what they all share is that they determine an execution pathway for the program. Python has relatively few forms of flow control. They are conditionals, exceptions, and loops.

As someone primarily interested in physical reality, you might wonder why you should care about flow control and logic. In some ways, this is like asking why arithmetic is important. Logic presents rules that allow you to build up and represent more complex ideas. This enables the physics modeling you want to do by giving you a means to express the choices and behavior of your model to the computer. With basic flow control syntax, your models can make simple decisions. With more advanced flow control, your models can make more sophisticated choices more easily. In other situations, flow control allows you to reuse the same code many times. This makes the software model faster to write and easier to understand, because it has fewer total lines of code. Logic and flow control are indispensible to doing any significant amount of work with computers. So, without further delay, let’s jump into conditionals, our first bit of flow control.

Conditionals

Conditionals are the simplest form of flow control. In English, they follow the syntax “if x is true, then do ...