dmitrey wrote:
hi all,
I have a class (FuncDesigner oofun) that has no attribute "size", but
it is overloaded in __getattr__, so if someone invokes
"myObject.size", it is generated (as another oofun) and connected to
myObject as attribute.
So, when I invoke in other code part "hasattr(myObject, 'size')",
instead o returning True/False it goes to __getattr__ and starts
constructor for another one oofun, that wasn't intended behaviour.
Thus "hasattr(myObject, 'size')" always returns True. It prevents me
of some bonuses and new features to be done in FuncDesigner.
'size' in dir(b)
False
hasattr(b,'size')
True
'size' in dir(b)
True
Could you fix it?
Quite simple, when calling b.size, return the computed value but do not
set it as attribute, the value will be computed on each b.size call, and
hasattr w. If you don't want to compute it each time, cause there no
reason for it to change, use a private dummy attribute to record the
value instead of size (__size for instance) and return the value of
__size when getting the value of size.
class Foo(object):
def __init__(self):
self.__size = None
def __getattr__(self, name):
if name == "size":
if self.__size is None:
self.__size = 5 # compute the value
return self.__size
raise AttributeError(name)
b = Foo()
print 'size' in dir(b)
print hasattr(b, 'size')
print 'size' in dir(b)
False
True
False
JM
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