### The suggested superclass ###
class AutoInit (object) :
"""
Each class that inherits from AutoInit (directly or indirectly) can
specify all standard attributes and their initials in dictionary called
classinitials.
Important: if used, it is recommended to specify an attribute with default value None (for copy constructor)
"""
def get_initials(self):
# list of classes in inheritance list (superclasses first)
# care should be taken with multiple inheritance,
# if unsure of class heirachy then overide all initials in originating class.
clss = list(self.__class__.__mro__)
clss.reverse()
initials = {}
for cls in clss:
if hasattr(cls,'classinitials'):
initials.update(getattr(cls,'classinitials'))
return initials
initials = property( get_initials )
def __init__(self, *args, **kwargs) :
# check that the class-attribute 'classinitials' exists
if not hasattr(self, 'initials') : return
# if arg is same type as this then copy construct
if len(args) > 0 and self.__class__ == args[0].__class__ :
arg = args[0] # first element in args is now object to copy
# for each attribute in classinitials copy from arg.attribute to this.attribute
for attribute in self.initials :
setattr(self, attribute, getattr(arg, attribute))
# where args is empty or first arg is not of same class then ignore.
# insted copy all present managed attributes from kwargs dictionary
# where not present get default from initials dictionary.
else :
for attribute in self.initials :
if attribute in kwargs :
setattr(self, attribute, kwargs[attribute])
else :
setattr(self, attribute, self.initials[attribute])
def get_managed_dict(self):
"""
Returns a dictionary of objects attributes, where attribute names are given in self.initials
"""
return dict([ (k,getattr(self,k)) for k in self.initials ])
def __str__(self):
return str(self.get_managed_dict())
### example subclasses ###
class A(AutoInit):
classinitials = { 'attr1' : 'set from A' }
def __init__(self,*args,**kwargs):
AutoInit.__init__(self,*args,**kwargs)
class B(A):
classinitials = { 'attr2' : 'set from B' }
def __init__(self,*args,**kwargs):
A.__init__(self,*args,**kwargs)
class C(B):
classinitials = { 'attr1' : 'set from C',
'attr3' : 'set from C' }
def __init__(self,*args,**kwargs):
B.__init__(self,*args,**kwargs)
### example usage ###
def test():
a = A()
b = B()
c1 = C()
c2 = C(attr1='set by constructor argument to c2')
c3 = C(c2)
print "Initialised objects:"
print "a:",a
print "b:",b
print "c1:",c1
print "c2:",c2
print "c3:",c3
print
## objects can then be used normally ##
c1.attr1 = 'set externally'
print "After manual set operation:"
print "c1:",c1
### run from command line if you like ###
if __name__ == '__main__':
test()
Diff to Previous Revision
--- revision 2 2010-07-20 15:03:13
+++ revision 3 2010-07-20 15:04:52
@@ -30,8 +30,8 @@
for attribute in self.initials :
setattr(self, attribute, getattr(arg, attribute))
# where args is empty or first arg is not of same class then ignore.
- # insted copy all present classinitials from kwargs dictionary
- # where not present get default from classinitials dictionary.
+ # insted copy all present managed attributes from kwargs dictionary
+ # where not present get default from initials dictionary.
else :
for attribute in self.initials :
if attribute in kwargs :
