[Python-ideas] C# style properties

July 12, 2007

      Hello!

In the past few months I've been toying around with .NET, C# and
PythonNet. While I still think that C# is too wory (public static
explicit operator Egg(Spam spam) { ... }) C# has one syntax feature I
really like to see in Python.

private float _a
public float a
{
    get { return _a; }
    set { _a = value; }
}

I think it's a very nice way to define a variable that acts similar to
Python properties. get, set and value are part of the syntax.

Python has no nice way to define a property with set and get. You always
have to use lambda or some private methods.

class Now:
    _a = 0.0
    @property
    def a(self):
        """Read only property
        return self._a

    def _geta(self):
        return self._a
    def _seta(self, value):
        self._a = value
    a = property(_geta, _seta)

It puts a lot of methods into the body of the class that are only used
for properties. I find the C# syntax more intriguing. It puts the getter
and setter into a block of their own and makes reading and understand
the property more easy.

What do you think about this syntax?

class EasyExample:
    _a = 0.0
    property a:
        """doc string
        """
        def get(self) -> float:
            return self._a
        def set(self, value):
            self._a = float(value)
        def delete(self):
            del self._a

It may be possible to combine the feature with generic methods but I
guess that's not going to be easy.

class ComplexExample:
    _a = 0.0
    property a:
        """doc string
        """
        def get(self) -> float:
            return self._a

        @generic
        def set(self, value:float):
            self._a = value

        @generic
        def set(self, value:int):
            self._a = float(value)

        @generic
        def set(self, value:str):
            self._a = float(value)

        def delete(self):
            del self._a

An alternative syntax. It doesn't look as clean as the other syntax but
has the benefit that the variable is in front of the definition.

class AlternativeSyntax:
    _a = 0.0
    a = property:
        """doc string
        """

Comments?

Christian

[Python-ideas] C# style properties

Christian Heimes