13.2 终止程序并给出错误信息

问题

You want your program to terminate by printing a message to standard error and re‐turning a nonzero status code.

解决方案

To have a program terminate in this manner, raise a SystemExit exception, but supplythe error message as an argument. For example:

raise SystemExit(‘It failed!')

This will cause the supplied message to be printed to sys.stderr and the program toexit with a status code of 1.

讨论

This is a small recipe, but it solves a common problem that arises when writing scripts.Namely, to terminate a program, you might be inclined to write code like this:

import syssys.stderr.write(‘It failed!n')raise SystemExit(1)

None of the extra steps involving import or writing to sys.stderr are neccessary if yousimply supply the message to SystemExit() instead.