----- Original Message -----
> From: "ast" <[email protected]>
> I have the idea to write:
>
> def __init__(center=(0,0), radius=10, mass=None)):
>
> if mass == None:
> self.mass = radius**2
> else:
> self.mass = mass
>
> but maybe Python provides something clever.
>
> Thx
If you like one-liners,
def __init__(self, center=(0,0), radius=10, mass=None):
self.center = center
self.radius = radius
self.mass = (mass is None and radius**2) or mass
But there's an issue with that solution: self.mass being computed during the
instance initialization, what if radius is changing ?
c1 = Circle((0,0), 10, None)
print c1.mass
20
c1.radius = 20
print c1.mass
20 # that is unexpected
Everytime an attribute is computed from another attribute, it should ring a
python bell : property
def __init__(self, center, radius, mass):
self.center = center
self.radius = radius
self._mass = mass
@property
def mass(self):
return self._mass if self._mass is not None else self.radius*2
c1 = Circle((0,0), 10, None)
print c1.mass
20
c1.radius = 20
print c1.mass
40
JM
Note : what is the mass of a circle ?
-- IMPORTANT NOTICE:
The contents of this email and any attachments are confidential and may also be
privileged. If you are not the intended recipient, please notify the sender
immediately and do not disclose the contents to any other person, use it for
any purpose, or store or copy the information in any medium. Thank you.
--
https://mail.python.org/mailman/listinfo/python-list
