On 2018-09-06 16:00, MRAB wrote:
> On 2018-09-06 21:24, Michael F. Stemper wrote:
>> On 2018-09-06 09:35, Rhodri James wrote:
>>> Is it worth creating the superclass in Python? It sounds like it's a
>>> bit marginal in your case. I'm not that seasoned in object-oriented
>>> design either, but my yardstick would be how much common code does it
>>> eliminate?
>>
>> About half a dozen lines. Here's the common part:
>>
>> def __init__( self, xmlmodel, V, id ):
>>
>> try:
>> P_0s = xmlmodel.findall( 'RatedPower' )[0].text
>> self.P_0 = float( P_0s )
>> except:
>> Utility.DataErr( "Power not specified for %s load" % (id) )
>> if self.P_0<=0.0:
>> Utility.DataErr( "Power for %s load must be postive, not %s" \
>> % (id,P_0s) )
> A word of advice: don't use a "bare" except, i.e. one that doesn't
> specify what exception(s) it should catch.
Given that I moved the first line ("P_0s = ...") out of the "try"
clause, does this align with your advice?
# If pre-validation has been run, guaranteed to have RatedPower
P_0s = xmlmodel.findall( 'RatedPower' )[0].text
try:
self.P_0 = float( P_0s )
except ValueError:
Utility.DataErr( "Power for %s load, '%s', not parsable" \
% (id,P_0s) )
if self.P_0<=0.0:
Utility.DataErr( "Power for %s load must be postive, not %s" \
% (id,P_0s) )
> Your try...except above will catch _any_ exception. If you misspelled a
> name in the 'try' part, it would raise NameError, which would also be
> caught.
In another case where I had a "bare exception", I was using it to see if
something was defined and substitute a default value if it wasn't. Have
I cleaned this up properly?
try
id = xmlmodel.attrib['name']
except KeyError:
id = "constant power"
(Both changes appear to meet my intent, I'm more wondering about how
pythonic they are.)
--
Michael F. Stemper
Isaiah 10:1-2
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