On 02/26/2018 07:28 AM, Rhodri James wrote:
On 26/02/18 14:41, Steven D'Aprano wrote:
I have a class with a large number of parameters (about ten) assigned in
`__init__`. The class then has a number of methods which accept
*optional* arguments with the same names as the constructor/initialiser
parameters. If those arguments are None, the defaults are taken from the
instance attributes.
An example might be something like this:
class Foo:
def __init__(self, bashful, doc, dopey, grumpy,
happy, sleepy, sneezy):
self.bashful = bashful # etc
def spam(self, bashful=None, doc=None, dopey=None,
grumpy=None, happy=None, sleepy=None,
sneezy=None):
if bashful is None:
bashful = self.bashful
if doc is None:
doc = self.doc
if dopey is None:
dopey = self.dopey
if grumpy is None:
grumpy = self.grumpy
if happy is None:
happy = self.happy
if sleepy is None:
sleepy = self.sleepy
if sneezy is None:
sneezy = self.sneezy
# now do the real work...
def eggs(self, bashful=None, # etc...
):
if bashful is None:
bashful = self.bashful
# and so on
There's a lot of tedious boilerplate repetition in this, and to add
insult to injury the class is still under active development with an
unstable API, so every time I change one of the parameters, or add a new
one, I have to change it in over a dozen places.
Is there a good fix for this to reduce the amount of boilerplate?
You could use dicts? Untested code:
class Foo:
def __init__(self, **kwds):
self.defaults = kwds
def spam(self, **kwds):
vars = self.defaults.copy()
vars.update(kwds)
# Do the work with vars['bashful'] etc
That's what I was about to suggest (and equally fail to test). It at
least segregates the set of "instance variables I want to have
auto-default behavior" from the rest of them. Yeah, **kwargs is clumsy,
but it gets the job done.
--
Rob Gaddi, Highland Technology -- www.highlandtechnology.com
Email address domain is currently out of order. See above to fix.
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