__init__ style questions
will at willmcgugan.com
Mon Oct 2 06:42:01 EDT 2006
I am writting a Vector3D class as a teaching aid (not for me, for
others), and I find myself pondering over the __init__ function. I want
it to be as easy to use as possible (speed is a secondary
Heres the __init__ function I have at the moment.
__slots__ = ('x', 'y', 'z')
def __init__(self, x_or_iter=None, y=None, z=None):
if x_or_iter is None:
self.x = self.y = self.z = 0
elif z is None:
it = iter(x_or_iter)
self.x = float(it.next())
self.y = float(it.next())
self.z = float(it.next())
self.x = float(x_or_iter)
self.y = float(y)
self.z = float(z)
A Vector3D can be constructed in 3 ways. If no parameters are given it
assumes a default of (0, 0, 0). If one parameter is given it is assumed
to be an iterable capable of giving 3 values. If 3 values are given
they are assumed to be the initial x, y, z.
And now for the ponderings...
1) Is 'overloading' like this pythonic, or should I supply alternative
2) I convert the input values to floats, which seems convenient because
a Vector could be constructed with integers and other objects capable
of being converted to floats. Could this hide errors?
3) I like the constructing from an iterable, but it does mean that I
can do something crazy like Vector3D("123"). Could this also hide
4) This does seem like a good candidate for __slots__, since there will
could be large-ish lists of Vector3Ds. But is it a premature
If it was just for myself or other experienced programmers I wouldn't
be bothered about having the ability to do stupid things, because I
simply wouldnt do them! But I dont want to teach beginner programmers
Any comments appreciated...
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