I am using Python 3.8.6 and this works fine
class A:
@property
def _a(self):
return getattr(self, '_a_', 0)
@_a.setter
def _a(self, value):
self._a_ = value
a = A()
print(a._a) # prints 0
a._a = 10
print(a._a) # prints 10 as expected
This doesn't work
class A:
@property
def _a(self):
return getattr(self, '__a', 0)
@_a.setter
def _a(self, value):
self.__a = value
a = A()
print(a._a) # prints 0
a._a = 10
print(a._a) # prints 0 again
That's mind blowing! the only difference between the first and second example is that the private attribute is __a
instead of _a_
Any idea why? I wasn't able to figure it out
It due to private name mangling . The fix is simple:
class A:
@property
def _a(self):
return getattr(self, '_A__a', 0)
@_a.setter
def _a(self, value):
self.__a = value
a = A()
print(a._a) # prints 0
a._a = 10
print(a._a) # prints 10 now
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