On 10/15/2012 12:22 PM, John Gordon wrote:
In <mailman.2217.1350317845.27098.python-l...@python.org> MRAB
<pyt...@mrabarnett.plus.com> writes:
Why wasn't the message printed out?
You didn't add a __str__ method:
class PvCamError(Exception):
def __init__(self, msg):
self.msg = msg
def __str__(self):
return self.msg
Wouldn't PvCamError inherit __str__() from Exception?
Exception instances get a .args attibute set to the arguments of the
class call and printed in the .__str__ message.
>>> dir(Exception())
['__cause__', '__class__', '__context__', '__delattr__', '__dict__',
'__dir__', '__doc__', '__eq__', '__format__', '__ge__',
'__getattribute__', '__gt__', '__hash__', '__init__', '__le__',
'__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__',
'__repr__', '__setattr__', '__setstate__', '__sizeof__', '__str__',
'__subclasshook__', '__suppress_context__', '__traceback__', 'args',
'with_traceback']
>>> Exception('abc', 1)
Exception('abc', 1)
So class MyError(Exception) will get that basic default behavior. For
fancier printing, one needs a fancier .__str__ method ;-).
--
Terry Jan Reedy
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