Setting up an editor for programming

An editor is a program that lets us write longer programs than we can write on the >>> prompt. Then we can save the programs to files and run them as many times as we want without writing them again.

When programmers say "editor" they don't mean programs like Microsoft Word or LibreOffice/OpenOffice Writer. These programs are for writing text documents, not for programming. Programming editors don't support things like bigger font sizes for titles or underlining bits of text, but instead they have features that are actually useful for programming, like automatically displaying different things with different colors.

If you are on Windows or Mac OSX you have probably noticed that your Python came with an editor called IDLE. We are not going to use it because it's lacking some important features, and most experienced programmers (including me) don't use it or recommend it to anyone.

In this chapter we'll download, install, set up and learn to use a better editor. The setup part will take some time, but it's worth it and correct settings will help you avoid many problems later.

Which editor should I use?

These instructions are written for an editor called Geany. Its default settings are actually not very good for writing Python code, but you will learn to change the settings so you won't have trouble with switching to another editor later if you need to.

Different programmers have different favorite editors that they use, and the choice of editor is a very personal thing. You can use almost any editor you want if you make sure that you change its settings the same way we change Geany's settings in this tutorial.

Bad editors

Skip this part if you are going to use Geany.

But some editors are not good enough for actually making something with them. These editors cannot be set up using these instructions because they don't have some of the features we need, so don't use these editors for writing Python:

Gedit
IDLE
Nano
Notepad
Pluma
Wingware

On the other hand, some editors have too many features for getting started with programming. They are not bad, but they are not meant for beginners. So I don't recommend using these editors yet:

Emacs
NetBeans
PyCharm
Spyder
Vim

These lists don't contain all bad editors, but these are editors that people often try to use. If you know a bad editor and you think I should mention it here, please let me know.

Installing your new editor

Installing Geany is easy. If you are using Windows or Mac OSX, go to the official Geany download page and click the correct download link. If you are using Linux, just install Geany from the package manager like any other program. For example, on Debian-based distributions (e.g. Ubuntu) you can type sudo apt install geany on a terminal.

When you have Geany installed, you can launch it like any other program. By default, it has a big sidebar and bottom area, but we don't need them so you can start by dragging them away. Geany should look roughly like this after that:

Dark background

Geany has a white background by default, but we'll tell Geany to use a black background instead. Your eyes will thank you for doing this when you have been programming for a few hours.

Click Edit at top and click Preferences.
Click Editor at left.
Click Display at top right.
Check Invert syntax highlighting colors.
Click OK.

If you don't like the colors, you can install more color schemes and then go to View at top and click Change Color Scheme.

Opening and saving files

Now it's time to create our first file. Geany creates a new file when you open it for the first time, but it doesn't know that it's going to be a Python file. We need to tell that to Geany by saving the file first. You can use the File menu at top or the buttons below the menus, just like in most other programs.

Save the empty file on your desktop as test.py. The .py at the end of the name is important, it tells Geany and other programs that it's a Python file.

Automatic tab expanding

Open a Python file in your editor. Then press the tab key, and the cursor should move right. Now press the left arrow key. See how the cursor jumps over the empty space? The empty space is actually a tab character, but Python's style guide recommends using four spaces instead of tab characters so we'll need to change Geany's settings.

Click Edit at top, then click Preferences.
Click Editor at left.
Click Indentation at top.
Select Spaces instead of Tabs.
Click OK.
Click Project at top and click Apply Default Indentation.

Delete the whitespace, then press tab and press the arrow left again. Now the cursor should move one space at a time.

TODO: animated gifs that show what's going on.

Stripping spaces when pressing Enter

Press Tab and then press Enter, and Geany should add spaces to the new line automatically for you. If you are not using Geany, make sure that your editor does this too.

Now press the arrow up and then move left and right. You'll notice that the previous line has spaces left over on it. Leaving useless spaces to ends of lines like this is usually considered bad style, but it's easy to tell Geany to get rid of them:

Click Edit at top and click Preferences
Click Editor at left.
Click Features at top.
Check Newline strips trailing spaces.
Click OK.

Press tab and Enter again. If you go back to the previous line now there is no whitespace on it.

TODO: again, animated gifs

Maximum line length

You have probably noticed that Geany displays a thin, green-ish line at right from where you type. The idea is that you should avoid writing anything longer than where this line is. Your programs will work if they contain lines that go past this marker, but it's not recommended because shorter lines are nicer to work with in general. People with small screens can work with your code, and people with large screens can have multiple files opened at the same time.

By default, there's room for 72 characters before the marker. Staying in 72 characters is not always easy, and that's why Python's style guide recommends 79 instead of 72. Let's move Geany's marker to 79 characters:

Click Edit at top and click Preferences
Click Editor at left.
Click Display at top.
Change 72 to 79.
Click OK.

Running things from the editor

This setting up stuff is boring! Let's write some code.

We'll use this program to check if our editor is set up correctly. Create a new file and type this into it:

import sys
print(sys.version)

You don't need to understand this program yet, you'll learn what it does later in this tutorial. You can type this program on the >>> prompt to see what it does if you want to.

Now save the program somewhere as test.py. It doesn't matter what the name of the file is, but it needs to end with .py. This way Geany knows that it's a Python file.

Next we'll need to change Geany's settings so that it runs the program correctly. You need to have a Python file opened to change these settings.

Click Build at top, then click Set Build Commands.
The Execute command is probably python "%f". Change it to py "%f" if you are using Windows and python3 "%f" if you are using Linux or Mac OSX.
Click OK.

Note that the first part of our Execute is the same thing we type on a PowerShell or terminal. Actually the whole command means "run this file using my Python".

Now press the F5 key at the top of your keyboard to run the file we wrote. It should open up in a terminal or command prompt and print the same Python version as the >>> prompt prints when we open it. If the version starts with 2 it's too old, and you can ask me or some other experienced programmer for help.

Important notes

Now your editor is ready to go. There are a couple important things that you need to keep in mind when reading the rest of this tutorial:

When a code example starts with >>>, type it to the >>> prompt. If it doesn't, create or open a .py file with your editor, type the code into it and run the file.
When we type some code to the >>> prompt it echoes back the result when it's not None, but code in a file does nothing to the result. For example, typing 1 + 2 to the >>> prompt makes it echo 3, but we need to do print(1 + 2) if we want to do the same thing in a file.
The editor doesn't replace the >>> prompt. The prompt is good for trying things out quickly, and the editor is better when we want to write longer programs.

You're done!

This probably felt like a lot of work, but don't worry, there will be no more things like this in the future. Now we have installed and set up all the tools we need and we can continue learning Python.

If you have trouble with this tutorial please tell me about it and I'll make this tutorial better. If you like this tutorial, please give it a star.

You may use this tutorial freely at your own risk. See LICENSE.

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