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  1. class MyDesc(object):
  2.  
  3.     def __init__(self):
  4.         self.val = None
  5.  
  6.     def __get__(self, instance, owner):
  7.         print "MyDesc.__get__"
  8.         return self.val
  9.  
  10.     def __set__(self, instance, value):
  11.         print "MyDesc.__set__"
  12.         self.val = value
  13.  
  14. class MyObj(object):
  15.  
  16.     foo = MyDesc()
  17.  
  18.     def __init__(self, bar):
  19.         object.__setattr__(self, 'names', dict(
  20.             bar=bar,
  21.         ))
  22.         object.__setattr__(self, 'new_names', dict())
  23.  
  24.     def __setattr__(self, name, value):
  25.         print "MyObj.__setattr__ for %s" % name
  26.         try:
  27.             object.__getattribute__(self, name)
  28.         except AttributeError:
  29.             print 'New name', name, value
  30.             self.new_names[name] = value
  31.         else:
  32.             object.__setattr__(self, name, value)
  33.  
  34.     def __getattr__(self, name):
  35.         print "MyObj.__getattr__ for %s" % name
  36.  
  37.         if name in self.new_names:
  38.             return self.new_names[name]
  39.  
  40.         if name in self.names:
  41.             return self.names[name]
  42.  
  43.         raise AttributeError(name)
  44.  
  45. if __name__ == "__main__":
  46.     o = MyObj('bar-init')
  47.     o.quux = 3
  48.     print 'dict', o.__dict__
  49.     print 'new_names', o.new_names
  50.     print 'o.quux', o.quux
  51.     print "o.new_names['quux']", o.new_names['quux']
Success #stdin #stdout 0.03s 6356KB
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Standard input is empty
stdout
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MyObj.__setattr__ for quux
New name quux 3
dict {'new_names': {'quux': 3}, 'names': {'bar': 'bar-init'}}
new_names {'quux': 3}
o.quux MyObj.__getattr__ for quux
3
o.new_names['quux'] 3
https://ideone.com/XXAR5
language:
Python (cpython 2.7.16)
created:
12 years ago
visibility:
public

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