fget is a function for getting an attribute value. fset is a function for setting an attribute value. fdel is a function for deleting an attribute value. And doc creates a docstring for the attribute.
A typical use is to define a managed attribute x:
class C: def __init__(self): self._x = None def getx(self): return self._x def setx(self, value): self._x = value def delx(self): del self._x x = property(getx, setx, delx, "I'm the 'x' property.")
If c is an instance of C, c.x will invoke the getter, c.x = value will invoke the setter, and del c.x the deleter.
If given, doc will be the docstring of the property attribute. Otherwise, the property will copy fget ’s docstring (if it exists). This makes it possible to create read-only properties easily using property() as a decorator:
class Parrot: def __init__(self): self._voltage = 100000 @property def voltage(self): """Get the current voltage.""" return self._voltage
The @property decorator turns the voltage() method into a “getter” for a read-only attribute with the same name, and it sets the docstring for voltage to “Get the current voltage.”