"jeremito" <[EMAIL PROTECTED]> escribió en el mensaje
news:[EMAIL PROTECTED]
> Please excuse me if this is obvious to others, but I can't figure it
> out. I am subclassing dict, but want to prevent direct changing of
> some key/value pairs. For this I thought I should override the
> __setitem__ method as such:
> if key == 'xT':
> raise AttributeError("""Can't change xT. Please change,
> xF, xS, or xG""")
Why using a dictionary? I'd use a simple class with properties:
py> class Xs(object): # class names should be Uppercase
... def __init__(self, xS=1.0, xF=1.0, xG=1.0, nu=1.0, debug=0):
... self.xS = xS
... self.xF = xF
... self.nu = nu
... self.xG = xG
... xA = property(fget=lambda self: self.xG + self.xF)
... xT = property(fget=lambda self: self.xA + self.xS)
...
py> xs = Xs(1.0, 0.95, 0.80, 0.70)
py> print xs.xG
0.8
py> print xs.xA
1.75
py> print xs.xT
2.75
py> xs.xG = 0.5
py> print xs.xA
1.45
py> print xs.xT
2.45
py> xs.xA = 1.5
Traceback (most recent call last):
File "<stdin>", line 1, in ?
AttributeError: can't set attribute
py> xs.xT = 1.2
Traceback (most recent call last):
File "<stdin>", line 1, in ?
AttributeError: can't set attribute
py>
--
Gabriel Genellina
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