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Creating a Subdirectory

00:00 So you’ve created a new notes directory, but in here you want to keep track of plans on a different schedule. Let’s say you have monthly plans and weekly plans.

00:10 So you want to create a subdirectory to this notes directory that is inside of yet another subdirectory called plans. Let me type this out. It will be a little easier to understand.

00:21 So, say you want a monthly_dir and it should be inside of your notes_dir and then inside of a "plans" directory, and then it should be called "monthly".

00:36 This is where you’re going to store your monthly plans, let’s say. Now you can create this path just like this.

00:44 No complaints. The path shows up beautifully. But now if you want to create this directory, you’ll run into an error. monthly_dir.mkdir() gives you a FileNotFoundError because, while the notes directory exists, you did not yet create the plans directory. In general, to be able to create a directory, all the parent directories need to already exist. However, there’s a different way of doing it by setting another parameter to True.

01:16 It goes like this. If you say monthly_dir.mkdir() and then pass parents the value True,

01:28 then you see that Python doesn’t complain, and monthly_dir does now exist. So all the intermediate subfolders—in this case, it’s only one, called "plans"—get created if you pass parents=True to .mkdir(). So putting these two things together, the one you saw before about exist_ok, and parents gives you a common pattern when creating directories using Python’s pathlib module. Let’s make a new directory.

02:00 So aside from your monthly plans, you also want to have weekly plans. So weekly_dir

02:14 "plans" and then "weekly".

02:17 And even if the subfolder "plans" wouldn’t exist, now you could create everything you need like this: saying weekly_dir.mkdir() and give it parents=True and exist_ok also True.

02:37 This is a common pattern, where you set both the .parents attribute as well as the .exist_ok attribute to True, but it might not make sense in all situations.

02:46 For example, if you want a user to pass a certain path, you might want to double check that the path already exists and that they’re not accidentally mistyping the path that they wanna save a file to, for example, just by adding an accidental typo. But you’ll commonly see, and probably also commonly use, this pattern of using parents=True and exist_ok also True. All right, enough with folders. In the next lesson, you’ll learn how to create files using pathlib.

James Tuttle on July 3, 2023

On your IDLE, how are you getting the intellsense popup?

Bartosz Zaczyński RP Team on July 4, 2023

@James Tuttle Those should work out of the box, for example, when you open a parenthesis and give IDLE a second before it shows the popup.

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