A front-end to Python that has powerful macro capabilities.

http://livelogix.net/logix/
For example, adding an "isa" operator:
{{{
[base]: defop 50 expr "isa" expr func ob typ:
      :     return isinstance(ob, typ)

[base]: 'a' isa str
True
}}}

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See also: BooLanguage, IronPython