In order to make an extension really clean looking I'm trying to implement the ">>" operator in python as a class method. I'm not sure how to go about it though. I don't want to have to create an instance since I am really operating on the class itself.
>>> class C:
... @classmethod
... def __rshift__(cls, other):
... print("%s got %s" % (cls, other))
...
>>> C.__rshift__("input")
__main__.C got input
>>> C() >> "input"
__main__.C got input
>>> C >> "input"
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for >>: 'classobj' and 'str'
Background information:
I am trying to implement views in the peewee ORM (Similar to Django). Peewee allows you to define database tables and their relations as classes, like so:
class Track(Model):
title = CharField()
artist = ForeignKeyField(Artist)
class Artist(Model):
name = CharField(unique = True)
location = ForeignKeyField(Location)
class Location(Model):
state = CharField(size = 2)
city = CharField()
Note: For clarity's sake the order is reversed.
I'm trying to extend this with an implementation of views. One of the most difficult parts is setting on a clean way to indicate the joins. So far I have implemented the following:
class Song(View):
title = Track.title
artist = Track.artist >> "name"
state = Track.artist >> "location" >> "state"
This is ok, but I would really like to eliminate the "." to further simplify:
class Song(View):
title = Track >> "title"
artist = Track >> "artist" >> "name"
state = Track >> "artist" >> "location" >> "state"
Which would you rather use? Or both?
As a side note, can anyone think of a good way to indicate a backwards join? Something like the following is a bit awkward for me:
class LocWithSong(View):
state = Location >> "state"
title = Location >> Track.title
Define the method on the metaclass.
class MC(type):
def __rshift__(self, other):
return something(self, other)
class C(object):
__metaclass__ = MC
print C >> None
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