Thonny
A lightweight Python IDE for beginners and teaching that includes a simplified interface, a Python runtime, variable views and step-by-step execution.
What Thonny is for
Thonny reduces the number of moving parts in a first Python lesson. It provides an editor, Shell, variable view and step-by-step debugger, so learners can see how a statement changes program state instead of relying only on the final output.
Know which Python runs the file
Desktop installers commonly include a Python runtime, while advanced users can select an external interpreter or virtual environment. A package installed into a different Python will not be visible to the active Shell. Check the interpreter indicator before diagnosing imports.
Keep practice projects small and recoverable
Save scripts in a dedicated folder, use meaningful filenames and test one concept at a time. Keep course materials, input files and generated output separate from the application directory, and make a copy before changing a lesson project.
Maintenance note
This page covers Thonny installation, interpreter selection, beginner scripts and step debugging. Content review date: 2026-08-23.
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Thonny installation, interpreter selection and first Python program
Start with the bundled Python runtime, save a tiny script and use the Shell and step debugger to connect source code with program state.
Before you start
- Select the Windows, macOS or Linux package; portable and installed builds can store configuration in different places.
- Beginners should use the bundled Python first instead of configuring several interpreters at once.
- Prepare a separate practice folder rather than keeping code in a system or application directory.
Installation steps
- 01
Install or extract Thonny
Complete the installer or extract the portable package to a stable directory. Do not run a script directly from a compressed archive window.
- 02
Confirm the active interpreter
Check the interpreter shown in the lower-right area or Shell settings. If using an external Python, verify that its executable still exists.
- 03
Create a practice folder
Save the first file in a dedicated folder with a clear name, then run it from the editor so the active path is easy to verify.
Quick start
- 01
Save and run a small script
Print a value, perform a simple calculation and save before running. Confirm that the Shell output belongs to the current file.
- 02
Observe variables
Create a number, string and list, then use the variable view to compare their values before and after an assignment.
- 03
Step through execution
Use the debugger to execute one line at a time and watch function calls and expressions change the program state.
Usage tips
- Confirm the interpreter before installing a third-party package through the built-in package manager.
- If a course requires a specific Python version, create a separate interpreter instead of replacing the bundled runtime.
- Read the final traceback line for the error type, then locate the first line in your own file that triggered it.
Troubleshooting and uninstall
Why is there no output after pressing Run?
Check that the file was saved, the intended tab is active and the script actually contains an output statement. Stop an unfinished Shell input before running again.
Why does the interpreter show as unavailable?
Switch back to the bundled runtime or select a valid Python executable. Moving a portable directory can invalidate an old absolute path.
- Back up practice codeCopy scripts and course notes to a separate location and verify that important files open independently of the application.
- Remove Thonny and optional dataUninstall through the operating system, then decide whether to remove preferences and caches after confirming that no lesson data is stored there.
Frequently asked questions
Is Python required separately after installing Thonny?
Common desktop installers include a Python runtime for beginners. Users who need another version can select an external interpreter or environment.
Why can a package be installed but still missing in a script?
The package may have been installed into a different Python. Check Thonny's active interpreter and install the package there, then restart the Shell.
What is the step debugger useful for?
It shows how each line, function call and expression changes program state, which is especially useful when the final output hides an earlier logic error.