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textual/docs/guide/devtools.md
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Devtools

Textual comes with a command line application of the same name. The textual command is a super useful tool that will help you to build apps.

Take a moment to look through the available sub-commands. There will be even more helpful tools here in the future.

textual --help

Run

You can run Textual apps with the run subcommand. If you supply a path to a Python file it will load and run the application.

textual run my_app.py

The run sub-command assumes you have an App instance called app in the global scope of your Python file. If the application is called something different, you can specify it with a colon following the filename:

textual run my_app.py:alternative_app

!!! note

If the Python file contains a call to app.run() then you can launch the file as you normally would any other Python program. Running your app via `textual run` will give you access to a few Textual features such as live editing of CSS files.

Console

When running any terminal application, you can no longer use print when debugging (or log to the console). This is because anything you write to standard output would overwrite application content, making it unreadable. Fortunately Textual supplies a debug console of its own which has some super helpful features.

To use the console, open up 2 terminal emulators. Run the following in one of the terminals:

textual console

You should see the Textual devtools welcome message:

In the other console, run your application using textual run and the --dev switch:

textual run --dev my_app.py

Anything you print from your application will be displayed in the console window.

Textual log

In addition to printing strings, Textual console supports more advanced formatting in logs. To write advanced logs import log from textual as follows:

from textual import log

You can logs strings, other Python data types which will be pretty printed in the console. You can also log Rich renderables.