Python – How to throw error and exit with a custom message in python

Use the subprocess module in the standard library:

import subprocess
subprocess.run(["ls", "-l"])

The advantage of subprocess.run over os.system is that it is more flexible (you can get the stdout, stderr, the "real" status code, better error handling, etc...).

Even the documentation for os.system recommends using subprocess instead:

The subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using this function. See the Replacing Older Functions with the subprocess Module section in the subprocess documentation for some helpful recipes.

On Python 3.4 and earlier, use subprocess.call instead of .run:

subprocess.call(["ls", "-l"])

Use:

>>> import datetime
>>> datetime.datetime.now()
datetime.datetime(2009, 1, 6, 15, 8, 24, 78915)

>>> print(datetime.datetime.now())
2009-01-06 15:08:24.789150

And just the time:

>>> datetime.datetime.now().time()
datetime.time(15, 8, 24, 78915)

>>> print(datetime.datetime.now().time())
15:08:24.789150

See the documentation for more information.

To save typing, you can import the datetime object from the datetime module:

>>> from datetime import datetime

Then remove the leading datetime. from all of the above.