Pseudo-properties

Many Wax controls have a number of methods starting with Get and Set: GetSize/SetSize, GetPosition/SetPosition, GetFont/SetFont, etc. This is one of the areas where you can clearly see the underlying C++: objects have various private attributes that can be set via separate getter and setter methods.

This is not very Pythonic, so in addition to these methods, it is also possible to set these attributes like they were properties. For x.SetFoo(y), you can substitute x.Foo = y, and for print x.GetFoo() you can say print x.Foo. The following constructs are equivalent:

widget.SetSize((100, 100))
widget.Size = (100, 100)

and:

print widget.GetSize()
print widget.Size

How it works

This construct does not use the properties that were introduced in Python 2.2. Rather, it uses __getattr__ and __setattr__ to look up names dynamically. Hence the name pseudo-properties. If a pseudo-property Foo is used, and there isn't an existing attribute with that name, then the mechanism looks if there are methods GetFoo or SetFoo (depending on if we're getting or setting the value). If found, the method is called (otherwise an AttributeError is raised).

Pseudo-properties will work "partially"; if a widget has a method GetThis, but not SetThis, then widget.This will work, but widget.This = 42 will not. They will also work automatically for user-defined methods whose names start with Get and Set.

Note that the names of pseudo-properties start with an uppercase letter. The reason is, that the names used are simply method names without the "Get" or "Set". So, for SetSize, the property name is Size, not size. (This is actually a Good Thing, since it distinguishes the properties from "real" attributes that Wax controls might have, whose names usually start with a lowercase letter.)

Restrictions

• Sometimes Set methods require more than one parameter. In such cases, there can be no valid pseudo-property. x.Foo = y requires a method SetFoo() that takes one parameter y. (Some methods, like SetSize() and SetPosition(), take a tuple rather than two parameters, so there is no problem using these.)

• Sometimes an object has methods whose names start with Get or Set, but what follows is not a valid identifier. ListBox.Set() does not produce a valid pseudo-property. Neither does CheckBox.Set3StateValue(), because 3StateValue is not a valid identifier. (Saying mycheckbox.3StateValue = 2 is not valid Python.)

• There is currently no way to delete a pseudo-property. Such a feature doesn't make much sense in Wax, since the actual attributes cannot be deleted anyway.