Program design

Visualize a program as machines and pipes sending data around.

Teagan's Poet

Bonus lessons are optional.

Let's write a basic transaction processing system (TPS - not that one). A TPS tracks business events, like sales, inventory control... the regular stuff of business operations.

Hey, Ray! Wanna do some coding?

Ray

Who, me?

The others are better at this.

Maybe, maybe not. Watching you work will help the people reading this learn from you.

Fu Wei Hsu's Jojo​

Structure diagrams

Often, variables are glue that sticks code chunks to together. Here's the code again:

Why is repeating code a problem?

Define functions before you use them

Ray

I tried this, and got the error NameError: name 'rect_area' is not defined.

Python (and most languages) have a way to wrap code up so it can be called repeatedly: functions.

A function is a piece of code with a name. Other code calls the function when it wants something done.

Let's take the name tag program we wrote at the beginning of the course.

Test user input to make sure it's valid.