Tim Peters wrote:
See the Python (language, not library) reference manual, section 3.3.8 ("Coercion rules"), bullet point starting with:
Exception to the previous item: if the left operand is an instance of a built-in type or a new-style class, and the right operand is an instance of a proper subclass of that type or class, ...
So that is settled then. Not the most likely place to investigate when one has just read that "Arguments to rich comparison methods are never coerced" in 3.3.1 ("Basic customization"), though.
<Heh - just reread this, and realised my reply below misses the point. You're right that the subsection heading is a little misleading. . .>
Nothing is getting coerced. It's just that "A binop B" gets translated to a method call differently depending on the types of A and B. The options being:
A.__binop__(B) # 1 - the usual case B.__binop__(A) # 2.1 - commutative op, and B is a proper subclass of A B.__rbinop__(A) # 2.2 - possibly non-commutative op, and B is a proper subclass of A
This is so that things like the following work:
.>>> class SillyAdd(long): .... __add__ = long.__mul__ .... __radd__ = __add__ .... .>>> a = SillyAdd(4) .>>> a .4L .>>> a + 5 .20L .>>> 5 + a .20L
Cheers, Nick. -- http://mail.python.org/mailman/listinfo/python-list
