In-depth understanding of the atexit module in python

atexit module is very simple. It only defines a register function to register a callback function when the program exits. We can do some resource cleanup operations in this callback function. The following article mainly introduces the relevant information of the atexit module in python. Friends in need can refer to it.

atexit module introduction

python atexit module defines a register function, which is used to register an exit function in the python interpreter , this function is automatically executed when the interpreter terminates normally, and is generally used to perform some resource cleanup operations. atexit executes these functions in the reverse order in which they were registered; for example, register A, B, C, and run them in the order C, B, A when the interpreter terminates.

Note: If the program crashes abnormally, or exits through os._exit(), the registered exit function will not be called.

Official documentation: https://docs.python.org/3.5/library/atexit.html

Register exit function

atexit.register(func, *args, **kargs)

Put func as the function to be executed on termination. Any optional arguments to be passed to func must be passed as arguments to register(). The same function and parameters can be registered multiple times.

When the program exits, the registered functions are called in first-in, last-out order. If an exception is thrown during the execution of the exit function, atexit will print the exception information and continue to execute the next callback until all exit functions are executed, and it will rethrow the last exception received.

Example

By decorator:

#!/usr/bin/env python
from atexit import register
def main():
 print('Do something.')
@register
def _atexit():
 print('Done.')
if __name__ == '__main__':
 main()

Non-decorator method:

#!/usr/bin/env python
from atexit import register
def main():
 #pass
 print('XX')
def goodbye(name, adjective):
 print('Goodbye, %s, it was %s to meet you.' % (name, adjective))

register(goodbye, 'Donny', 'nice')
# or:
# register(goodbye, adjective='nice', name='Donny')
if __name__ == '__main__':
 main()

Delete the exit function [generally not used]

> atexit.unregister(func)
>

Remove func from the list of functions that run when the interpreter is closed. After calling unregister(), when the interpreter is closed, func will not be called even if it has been registered multiple times. If func has not been registered, unregister() will do nothing.

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