Validation of parameters

[Terry Reedy]

Kless wrote:
> On 10 ago, 15:03, Paddy <paddy3... at googlemail.com> wrote:
>> If you just want the absense of _foo to raise an exception then why to
>> just reference self._foo and leave the hard work to ptyhon? Something
>> like:
>>
>>   self._foo
>>
>> If it is present then fine, if it is not then an exception is raised.

> It only was an example but I need show a better message.

The usual idiom is
try: self._foo
except AttrError as m: #3.0
   <better message>