[Python-Dev] Counting collisions for the win

[Victor Stinner]

> I'm surprised we haven't seen bug reports about it from users
> of 64-bit Pythons long ago

A Python dictionary only uses the lower bits of a hash value. If your
dictionary has less than 2**32 items, the dictionary order is exactly
the same on 32 and 64 bits system: hash32(str) & mask == hash64(str) &
mask for mask <= 2**32-1.