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 supply the 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 to exit 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 sys sys.stderr.write(‘It failed!n’) raise SystemExit(1)

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