Let’s use our problem-solving framework!
Understand the Problem: We want to write a program that prints a neat little message to the screen.
Devise a plan
Carry out the Plan: This is where we execute our plan. We’ll do that in the following sections.
Look Back: We’ll do this, below, as well. In future chapters, we’ll leave these last two off the number list and just do them in subsequent sections.
Let’s go!
Run IDLE as discussed in the previous chapter.
Once in there, we’re going to make a new file.
It used to be that everyone who used computers knew what a file was. But these days, many people use computers for years without encountering the concept.
So! A file is a collection of data with a name. Examples of files would be images, movies, PDF documents, music files, and so on.
The name indicates something about the contents of the file. Generally. It really can be anything, but that would be misleading, like labeling a box of raisins as “Chocolate”.
The name is split into two parts, commonly, separated by a period. The first part is the name, and the second part is the extension. Confusingly sometimes people refer to the name and extension together as the “name”, so you’ll have to rely on context.
Sometimes, depending on the system, the extension is optional.
As an example, here’s a complete file name and extension:
{.default} hello.pyThere we have a file named
helloand an extension.py. This is a common extension that means “this is a Python source code file”.
Pull down “File→New” and that’ll bring up a blank window.
And let’s enter some code!
Type the following6 into the editor (the line numbers, below, are for reference only and shouldn’t be typed in):
We’re (almost) ready to run!
Hit F5 from the editor window (you might have to hit fn-F5 on the Mac) to run the code. Alternately, you can pull down the “Run” menu and select “Run Module”.
If you haven’t saved the file, it will prompt you to save the file. (You can pull down “File→Save”, or hit COMMAND-S or CTRL-S to do this preemptively.)
Give it a good name, like hello.py.
And then, in the console window, you’ll see the output appear! [Angelic Chorus!]
Hello, world!
My name's Beej and this is (possibly) my first program!Did you miss it? Hit F5 again and you’ll see it appear again.
You just wrote some instructions and the computer carried it out!
Next up: write a Quake III clone!
Okay, so maybe there might be a small number of in between things that I skimmed over, but, as Obi-Wan Kenobi once said, “You’ve taken your first step into a larger world.”
Remember to use the four problem-solving steps to solve these problems: understand the problem, devise a plan, carry it out, look back to see what you could have done better.
dijkstra.py that prints out your three favorite Edsger Dijkstra quotes7.