CLI

In general, the py command passes on its arguments to the selected Python interpreter. Below are the Launcher-specific arguments that are supported.

Arguments

-[X]

Specifies the major Python version desired, e.g. -3. Specifying such a restriction causes the equivalent PY_PYTHON[X] environment variable to be used if set.

See the overview for more details.

-[X.Y]

Specifies the major and minor Python version desired, e.g. -3.6 for Python 3.6.

See the overview for more details.

--list

Lists all Python interpreters found on the PATH environment variable.

Environment variables

PY_PYTHON

Specifies a version restriction when none is specified on the command line, i.e. py is used. This is useful for setting the default Python version to always use.

See the overview for more details.

PY_PYTHON[X]

Specifies the version restriction when the equivalent major Python version is specified on the command line, e.g. -3 causes PY_PYTHON3 to be used if set.

See the overview for more details.

PYLAUNCH_DEBUG

When set, causes the Python Launcher to print out information about its interpreter search to stderr.