使Python的“assert”抛出一个我选择的异常 [英] Making Python's `assert` throw an exception that I choose

问题描述

我可以使 assert 抛出一个我选择的异常，而不是 AssertionError ？

Can I make assert throw an exception that I choose instead of AssertionError?

更新：

我会解释我的动机：到目前为止，我已经有断言风格测试引起了我自己的例外;例如，当您使用某些参数创建一个 Node 对象时，它会检查参数是否适合创建一个节点，如果不是，则会引发 NodeError 。

I'll explain my motivation: Up to now, I've had assertion-style tests that raised my own exceptions; For example, when you created a Node object with certain arguments, it would check if the arguments were good for creating a node, and if not it would raise NodeError.

但是我知道Python有一个 -o 模式，其中断言被跳过，我想提供，因为它会使我的程序更快。但我仍然希望有自己的例外。这就是为什么我要用自己的例外来使用断言。

But I know that Python has a -o mode in which asserts are skipped, which I would like to have available because it would make my program faster. But I would still like to have my own exceptions. That's why I want to use assert with my own exceptions.

推荐答案

这将工作。但是有点疯狂。

This will work. But it's kind of crazy.

try:
    assert False, "A Message"
except AssertionError, e:
    raise Exception( e.args )

为什么不这样？这不是很疯狂。

Why not the following? This is less crazy.

if not someAssertion: raise Exception( "Some Message" )

这只是一个比 assert 声明更小的一点，但不违反我们的期望

It's only a little wordier than the assert statement, but doesn't violate our expectation that assert failures raise AssertionError.

考虑这一点。

def myAssert( condition, action ):
    if not condition: raise action

然后你可以用或多或少地替换现有的断言。

Then you can more-or-less replace your existing assertions with something like this.

myAssert( {{ the original condition }}, MyException( {{ the original message }} ) )

一次你已经这样做了，你现在可以随意地启用或禁用或者你想要做的任何事情。

Once you've done this, you are now free to fuss around with enable or disabling or whatever it is you're trying to do.

另外，一个href =http://docs.python.org/library/warnings.html =noreferrer> warnings 模块。这可能正是你想要做的。

Also, read up on the warnings module. This may be exactly what you're trying to do.

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