I'm a bit new to Enthought traits module. I would like to specify a trait for which only a few floating-point values are allowed. Unfortunately, I can't use a Enum because it breaks the code base I'm working on. How can I specify which values are valid for a Float? Do I have to create another class deriving from Float with an overloaded validate?
Yes, the traits docs indicate that you should subclass the Float trait and add your custom validation code.
See the section about Custom Traits. I'd take a look at the source for the implementation of Enum as well.