Automatic comparison operators in python

order.py

class Order(object):
    __lt__ = lambda self, other: other > self
    __gt__ = lambda self, other: not self <= other
    __le__ = lambda self, other: other >= self
    __ge__ = lambda self, other: not self < other
    __ne__ = lambda self, other: self < other or other < self
    __eq__ = lambda self, other: not self != other

test_order.py

import operator, inspect

if __name__ == '__main__':
    # Test all operators work after inheriting Order and overriding only one
    OPS = ('lt', 'gt', 'le', 'ge')
    
    class Test(Order):
        def __init__(self, n):
            self.n = n
            
        __repr__ = lambda self: repr(self.n)

    def testClass(fname, f):
        return type('Test' + fname, (Test,), {
            fname: lambda self, other: f(self.n, other.n),
        })

    classes = [ testClass('__%s__' % op, getattr(operator, op)) for op in OPS ]

    def testOperators(a, b):
        for op in ("<", ">", "<=", ">=", "==", "!="):
            result  = eval("a " +op+ " b")
            correct = "OK" if result == eval("a.n " +op+ " b.n") else "ERROR"
            print "\t%(a)s %(op)s %(b)s\t%(result)s\t(%(correct)s)" % locals()
            
    for cls in classes:
        print "Testing " + cls.__name__
        testOperators(cls(1), cls(5))
        testOperators(cls(3), cls(3))
        testOperators(cls(8), cls(1))