python - 艰难地学习 Python - 练习 36 - if else die 函数

Question

If 语句的第二条规则 here ，这让我感到困惑:

If this else should never run because it doesn't make sense, then you must use a die function in the else that prints out an error message and dies, just like we did in the last exercise. This will find many errors.

这是上次练习的代码:

def dead(why):
    print why, "Good job!"
    exit(0)

def start():
    print "You are in a dark room."
    print "There is a door to your right and left."
    print "Which one do you take?"

    choice = raw_input("> ")

    if choice == ‘left’:
        bear_room()
    else:
        dead(‘You stumble around the room until you starve.’)

它的本质是说如果不满足条件就必须成功终止程序吗？

Answer 1

是的，这个想法是:

import sys

def die(msg):
  print msg
  sys.exit(1)

if condition:
  # do stuff
else:
  die('This cannot happen!')

您也可以使用 assert 代替，或引发异常，或任何其他会导致灾难性失败的事情。这有助于您在运行时验证您不希望执行的子句确实没有运行。

恕我直言，您不应该太在意这个die 是如何完成的。引用的文本试图说明的重点是，当您确定某些条件为真时，您不妨强行声明它，以便捕获运行时错误。