Installing Python
If Python is already installed on your system, fyn will detect and use it without configuration. However, fyn can also install and manage Python versions. fyn automatically installs missing Python versions as needed — you don't need to install Python to get started.
Getting started
To install the latest Python version:
Note
Python does not publish official distributable binaries. As such, fyn uses distributions from the Astral python-build-standalone project. See the Python distributions documentation for more details.
Once Python is installed, it will be used by fyn commands automatically. fyn also adds the
installed version to your PATH:
fyn only installs a versioned executable by default. To install python and python3
executables, include the --default option:
Tip
See the documentation on installing Python executables for more details.
Installing a specific version
To install a specific Python version:
To install multiple Python versions:
To install an alternative Python implementation, e.g., PyPy:
See the python install documentation
for more details.
Reinstalling Python
To reinstall fyn-managed Python versions, use --reinstall, e.g.:
This will reinstall all previously installed Python versions. Improvements are constantly being added to the Python distributions, so reinstalling may resolve bugs even if the Python version does not change.
Viewing Python installations
To view available and installed Python versions:
See the python list
documentation for more details.
Automatic Python downloads
Python does not need to be explicitly installed to use fyn. By default, fyn will automatically download Python versions when they are required. For example, the following would download Python 3.12 if it was not installed:
Even if a specific Python version is not requested, fyn will download the latest version on demand. For example, if there are no Python versions on your system, the following will install Python before creating a new virtual environment:
Tip
Automatic Python downloads can be easily disabled if you want more control over when Python is downloaded.
Note that when an automatic Python installation occurs, the python command will not be added to
the shell. Use fyn python install-shim to ensure the python shim is installed.
Using existing Python versions
fyn will use existing Python installations if present on your system. There is no configuration necessary for this behavior: fyn will use the system Python if it satisfies the requirements of the command invocation. See the Python discovery documentation for details.
To force fyn to use the system Python, provide the --no-managed-python flag. See the
Python version preference
documentation for more details.
Upgrading Python versions
Important
Support for upgrading Python patch versions is in preview. This means the behavior is experimental and subject to change.
To upgrade a Python version to the latest supported patch release:
To upgrade all fyn-managed Python versions:
See the python upgrade documentation
for more details.
Next steps
To learn more about fyn python, see the Python version concept
page and the command reference.
Or, read on to learn how to run scripts and invoke Python with fyn.