[Tutor] Checking for custom error codes

[wormwood_3]

> Traceback (most recent call last):
>  File "domainspotter.py", line 150, in <module>
>    runMainParser()
>  File "domainspotter.py", line 147, in runMainParser
>    td.run()
>  File "domainspotter.py", line 71, in run
>    checkdomains.lookup()
>  File "domainspotter.py", line 108, in lookup
>    from rwhois import WhoisRecord, NoSuchDomain
> ImportError: cannot import name NoSuchDomain
>
> Maybe I need to import something else to be able to throw it.
>
> I think if someone can explain a more general form of this I would be on 
> better footing: To use a custom error code (from a module) in a loop or 
> anywhere else, do I need to import the code itself? I had assumed that 
> once I imported the module that defined the error code, I could catch it 
> just like a core Python error code.

>>The problem is evident. The name NoSuchDomain is not defined. It is not a
>>variable. It is just a string. When you call an error like this raise
>>'NoSuchDomain', it's called something - don't know what (string
>>exception?) - but as you found out, that method of raising errors is now
>>frowned upon (deprecated). The way you are supposed to raise errors is to
>>create a new class, subclassing Exception. Then you would be able to catch
>>it by variable name as you are trying to do with the import. 

This is exactly what I needed, awesome! Looks like this is what you were saying to do?:
http://docs.python.org/tut/node10.html#SECTION0010500000000000000000

>>But you certainly can't import a constant string! It's like trying to import the
>>contents of a string variable, instead of the variable itself. Again, the
>>problem is deprecation, the rwhois will eventually have to be re-written so
>>that it uses exception classes, instead of just raising string errors.

That would seem best. I will see if they have this in the works.

Thanks again!