Elegant compare

[Jason Friedman]

class my_class:
    def __init__(self, attr1, attr2):
        self.attr1 = attr1 #string
        self.attr2 = attr2 #string
    def __lt__(self, other):
        if self.attr1 < other.attr1:
            return True
        else:
            return self.attr2 < other.attr2

I will run into problems if attr1 or attr2 is None, and they
legitimately can be.

I know I can check for attr1 or attr2 or both being None and react
accordingly, but my real class has ten attributes and that approach
will be long.  What are my alternatives?