On 12/2/2009 10:26 AM, allen.fowler wrote:
I've tried this, but have found two issues:
1) I can't set default values.
2) I can't set required values.
In both of the above cases, if the object is created without the
"exact" dict() I expect, all the assumption my methods make about what
is available in "self" fall apart.
You can inspect the dict, something like:
def __init__(self, **kwargs):
required = ['p1', 'p2', 'p3']
optional = {'p4': 'foo', 'p5': 'bar'}
if any(par not in kwargs for par in required):
raise TypeError('required parameter not set')
for par in optional:
if par not in kwargs:
kwargs[par] = optional[par]
# ... do work ...
Tips: turn this parameter checker into a @decorator
But generally, as Diez pointed out your class may be doing too much. Try
splitting it into smaller classes. Passing too much parameter is an
indication of a God Object (or demi-god)
http://en.wikipedia.org/wiki/God_object "He" just knows too much.
===
Unpythonic warning: Java-style code would use several separate
initializers that would be called in order before the object is in a
ready state (but never in an invalid state [!]). The first initializer
merely set all the attributes into some valid state. This is an
*anti-pattern* in python. Avoid it.
def __init__(self):
self.p1 = ''
self.p2 = 0
self.p3 = []
def init_name(self, name):
self.p1 = name
etc, etc...
===
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