Question

I defined a class:

class A:
    ''' hash test class
    >>> a = A(9, 1196833379, 1, 1773396906)
    >>> hash(a)
    -340004569

    This is weird, 12544897317L expected.
    '''
    def __init__(self, a, b, c, d):
        self.a = a
        self.b = b
        self.c = c
        self.d = d

    def __hash__(self):
        return self.a * self.b + self.c * self.d

Why, in the doctest, hash() function gives a negative integer?

Answer 1

It appears to be limited to 32-bits. By reading this question, it looks like your code might have produced the expected result on a 64-bit machine (with those particular values, since the result fits in 64 bits).

The results of the built-in hash function are platform dependent and constrained to the native word size. If you need a deterministic, cross-platform hash, consider using the hashlib module.