Part 2. Navigate to a declaration, implementation, and test

To be able to try the functionality described in this tutorial and follow it step by step, you'll need an example source code. It can be found here.

Navigating to declaration

Place the caret at the method feeds of the instance of the class Cat, and press Control+B. PyCharm jumps to the declaration of the method feeds, which is declared in the class Mammalia:

Navigating to implementation

Now, place caret at the declaration of the class Mammalia and try to find out which other classes implement it. To do that, press Control+Alt+B. You see a rather long list of classes implementing Mammalia:

Ok, choose whichever implementation you need (for example, Cow), and press Enter. PyCharm navigates to the selected implementation and places the caret at the class Cow declaration:

Should you select, for example Carnivorae, which resides in a separate file, this file would open in a separate editor tab.

Side note about pin

Presumably, you have already noticed the pin icon in the upper-right corner of the pop-up window. The same icon appears, for example, in the quick documentation lookup Control+Q. If you click this pin, the whole popup will be "pinned", which in the case of navigation and search means that all the encountered occurrences will be presented in the Find tool window.

Navigating with gutter icons

Now, let's look at the gutter. You see there a number of icons with the arrows pointing up or down. What does it mean?

If you hover your mouse pointer over an icon, PyCharm will show the list of child classes or overriding methods (in case of the down arrow), or the parent classes (in case of the up arrow):

What happens, if you click an icon? If a certain class is subclassed, or a method is overridden in more than one class, PyCharm will suggest to select the desired target from the list:

After that, PyCharm jumps to the selected target, and places the caret at the class (method) declaration. If there is only one superclass/subclass, or method, then such a navigation is done silently.

Jumping to a test

Note that testing functionality and setting up the test runner are out of scope of this tutorial. Refer to the section Run tests and Testing frameworks for details.

Place the caret at the class Cat in the file Mammalia.py. Then, press Control+Shift+T. You see the suggestion to create a test:

Summary

This brief tutorial is over. You've mastered the following features:

Navigating to a declaration.
Navigating to an implementation.
Using the gutter icons or to jump to an implementation or declaration.
Creating a test and jumping to it.

What's next?

Let's proceed with Part 3 and see how to find usages of a class or symbol.

Last modified: 28 February 2022