overview
The

Python program has two exits: os._exit() and sys.exit(). I looked up the difference between the two approaches.

os._exit() terminates the python program directly, and none of the code after that executes.

sys.exit() throws an exception: SystemExit, and if the exception is not caught, the python interpreter exits. If there is code to catch the exception, it will still execute.

for example

import os

try:
    os._exit(0)
except:
    print('Program is dead.')

this print does not print because no exception is caught.

import sys

try:
    sys.exit(0)
except:
    print('Program is dead.')
finally:
    print('clean-up')

Both print here because sys.exit() throws an exception.

Conclusion

exits the program gracefully by using sys.exit(), which raises a SystemExit exception, which we can then catch and do some cleanup. Os._exit () simply exits the Python interpreter, and none of the following statements are executed.

, in general, use sys.exit(); Os._exit () can be used in the child process produced by os.fork().

reference:

[1] https://docs.python.org/3.5/library/exceptions.html

[2] http://www.cnblogs.com/gaott/archive/2013/04/12/3016355.html