[myhdl-list] Re: VCD viewer ?

[Jan D. <ja...@ja...>]

Jean Demartini wrote:

> I'm a little newbie in Python and some Python idiom's are a little 
> puzzling. Then my question:
> 
> Why an enum variable is not a true class testable by isinstance(..,Enum) 
> ? this will simplify the catching of enum variables in _Signal.py.
> 
> Jean

I see your point, and I agree.

Probably the "idiom" that puzzles you is the usage of the "nested"
classes EnumItem and Enum in function enum in module _enum.py.
This looks rather strange: my intention was to make sure these
auxiliary classes are not directly usable by a user. But there
are other ways to achieve that, such as giving them a "private"
name, starting with underscore.

You are correct in stating that these objects should be
indentifiable by an instance check. This can be achieved easily
by using a "dummy" parent class, whose sole purpose is to be
subclassable by the actual (private) Enum class. This can be
done as follows (untested):

In _enum.py, create a new EnumType class at the module level:

     class EnumType(object):
         pass

Subclass the private Enum class from EnumType instead of object:

     class Enum(EnumType):
         ....

Make the EnumType class visible in __init__.py:

     from _enum import EnumType

Now you can use it with:

    from myhdl import EnumType

and things like isinstance(obj, EnumType) should work.

Regards,

Jan

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Jan Decaluwe - Resources bvba - http://jandecaluwe.com
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