A Python launcher is a single executable which uses a number of heuristics to locate a Python executable and launch it with a specified command line.

The Python launcher is py.exe which is found main directory in the standard install, as well as the ActiveState Python installs for Python 3.3 and later.

The py launcher—or just py for short—is a shortcut to all the installed versions of Python on your system. With a command-line switch, you can see at a glance all the Python interpreters you’ve installed and then invoke a specific version, whether it's 32-bit or 64-bit.