Does python have a "causes_exception()" function?

Question

I have the following code:

def causes_exception(lamb):
    try:
       lamb()
       return False
    except:
       return True

I was wondering if it came already in any built-in library?

/YGA

Edit: Thx for all the commentary. It's actually impossible to detect whether code causes an exception without running it -- otherwise you could solve the halting problem (raise an exception if the program halts). I just wanted a syntactically clean way to filter a set of identifiers for those where the code didn't except.

dF. · Accepted Answer · 2009-06-23 00:39:25Z

8

No, as far as I know there is no such function in the standard library. How would it be useful? I mean, presumably you would use it like this:

if causes_exception(func):
    # do something
else:
    # do something else

But instead, you could just do

try:
    func()
except SomeException:
    # do something else
else:
    # do something

answered Jun 23, 2009 at 0:39

dF.

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Comments

Alexander Lebedev · Accepted Answer · 2009-06-23 01:01:14Z

4

There's assertRaises(exception, callable) in unittest module and this is probably the only place where such check makes sense.

In regular code you can never be 100% sure that causes_exception you suggested are not causing any side effects.

answered Jun 23, 2009 at 1:01

Alexander Lebedev

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Comments

RichieHindle · Accepted Answer · 2009-06-23 00:38:30Z

2

I'm not aware of that function, or anything similar, in the Python standard library.

It's rather misleading - if I saw it used, I might think it told you without calling the function whether the function could raise an exception.

answered Jun 23, 2009 at 0:38

RichieHindle

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1 Comment

Josiah Over a year ago

I agree. Not that i've ever encountered such a method.

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