alexisl at hp.com
Mon Jan 5 14:44:50 CET 2015
Steven D'Aprano said on Mon, Jan 05, 2015 at 10:43:15PM +1100:
> Er, not really. What does distance mean in the context of classes? When
> would you use this? Can you give some examples, e.g. what's the distance
> between int and str?
Thanks for your fast response!
Distance means the number of classes in the inheritance hierarchy
between classes A and B. EG given a system:
A <-- B1 <-- B2 <-- D
class D(B2, C)
The distances should be:
A B1 B2 C D
A 0 None None None None
B1 1 0 None None None
src B2 2 1 0 None None
C 1 None None 0 None
D 2 2 1 1 0
> > def getclassdistance(srcs, dst):
> > """srcs may be either a single class or a list of (class, distance) pairs.
> > dst is the superclass to find.
> > Performs a breadth-first search for dst, returning the shortest distance.
> > """
Maybe the above could be inferred if this last line was changed to:
Performs a breadth-first search for dst, either through all the
bases of src (if a single class is given) or through the
bases of each class given by a pair.
Returns the minimal number of jumps required to reach a base class
equal to dst.
> > if type(srcs) != list:
> > srcs = [(srcs, 0)]
> > if len(srcs) == 0:
> > return None
> Shouldn't that be an exception?
It certainly could be. Does TypeError sound appropriate?
> > here, distance = srcs
> > if here == dst:
> > return distance
> > newSrc = srcs[1:] + [(c, distance + 1) for c in list(here.__bases__)]
> > return classDistance(newSrc, dst)
> What's classDistance?
Oops - the old method name. Should be getclassdistance.
Nova Engineer, HP Cloud. AKA lealexis, lxsli.
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