sys

How to find out where the interpreter is looking for importable modules?

The builtin module sys provides an access point to the Python environment. You find there command line arguments, the import path settings, the standard input, output and error stream and many more.

The sys.path variable contains the current directory, everything from the PYTHONPATH environment variable, and Pythons own folders.

import sys

print(sys.path)

How to call a Python program with command-line parameters?

The variable sys.argv contains a list of command-line arguments. The first one is usually the name of the called script.

print(sys.argv)

When you call this program with any of:

python script.py
python script.py hello world
python script.py 1 2 3

You should see a difference.

How to terminate a Python program gracefully?

The sys.exit() function ends execution of the Python interpreter immediately.

import sys

sys.exit()

.. seealso::

   `Documentation of the sys module <https://docs.python.org/3/library/sys.html>`__