How to terminate a Python script

Posted By: Teifion

I am aware of the die() command in PHP which exits a script early.

How can I do this in Python?

Solution

import sys
sys.exit()

details from the sys module documentation:

sys.exit([arg])

Exit from Python. This is implemented by raising the
SystemExit exception, so cleanup actions specified by finally clauses
of try statements are honored, and it is possible to intercept the
exit attempt at an outer level.

The optional argument arg can be an integer giving the exit status
(defaulting to zero), or another type of object. If it is an integer,
zero is considered “successful termination” and any nonzero value is
considered “abnormal termination” by shells and the like. Most systems
require it to be in the range 0-127, and produce undefined results
otherwise. Some systems have a convention for assigning specific
meanings to specific exit codes, but these are generally
underdeveloped; Unix programs generally use 2 for command line syntax
errors and 1 for all other kind of errors. If another type of object
is passed, None is equivalent to passing zero, and any other object is
printed to stderr and results in an exit code of 1. In particular,
sys.exit("some error message") is a quick way to exit a program when
an error occurs.

Since exit() ultimately “only” raises an exception, it will only exit
the process when called from the main thread, and the exception is not
intercepted.

Note that this is the ‘nice’ way to exit. @glyphtwistedmatrix below points out that if you want a ‘hard exit’, you can use os._exit(*errorcode*), though it’s likely os-specific to some extent (it might not take an errorcode under windows, for example), and it definitely is less friendly since it doesn’t let the interpreter do any cleanup before the process dies. On the other hand, it does kill the entire process, including all running threads, while sys.exit() (as it says in the docs) only exits if called from the main thread, with no other threads running.

Answered By: pjz

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