Hi,
I have what in my eyes seems a challenging problem.
Thanks to Peter Otten, i got the following code to work. It is a sort
of named tuple.
from operator import itemgetter
def constgetter(value):
def get(self): return value
return get
def createTuple(*names):
class TupleType(type):
pass
class T(tuple):
__metaclass__ = TupleType
def __new__(cls, *args):
if len(names) != len(args):
raise TypeError
return tuple.__new__(cls, args)
for index, name in enumerate(names):
setattr(T, name, property(itemgetter(index)))
setattr(TupleType, name, property(constgetter(index)))
return T
if __name__ == '__main__':
Point=makeTuple('x','y')
p=Point(4,7)
assert p.x==p[0]
assert p.y==p[1]
assert Point.x==0
assert Point.y==1
Now my problem is the following. I want to write a function called
createDerivedTuple in order to create a class derived from the one
created with the function createTuple, taking the parent class as first
argument:
def createDerivedTuple(parentclass,*names):
....... code yet to be figured out ....
The usage should be as follows:
DerivedPoint=makeDerivedTuple(Point,'z')
p=DerivedPoint(4,7,9)
assert p.x==p[0]
assert p.y==p[1]
assert p.z==p[2]
assert DerivedPoint.x==0
assert DerivedPoint.y==1
assert DerivedPoint.z==2
I am still a newbie on metaclasses but i am convinced there are elegant
solutions to this challenging problem.
Best regards
Alain
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