Claudio Grondi wrote: > Is there any deeper reason I don't understand > explaining why does min(A,B) behave different > for classes than for lists?
Yes, the sort order for lists is determined by their contents. With your example, the lists have identical contents, so min() returns the first minimum value encountered which is A for min(A,B) and B for min(B,A). For instances, the sort order is determined by custom __cmp__ or rich comparision methods. In the absence of those, the default ordering is determined by the object's id. In your example, the default is used and either object may be returned as the minimum depending on which object id is a higher number (that is an implementation and state dependent). Since the two objects have unique ids, min() will consistently find one to be lower than the other irrespective of argument order, if min(A,B) is A, then min(B,A) will also be A. The best way to develop your understanding here is view the object ids for the instances and experiment with the results of A<B, A<=B, A==B, etc. Then write a simple, pure python version of min() that returns the first occurence of the lowest valued element. Trace through its execution and all will become clear. Raymond -- http://mail.python.org/mailman/listinfo/python-list
