我想让自定义对象可哈希化(通过pickling)。我可以找到Python 2.x的__hash__
算法(请参见下面的代码),但它显然与Python 3.2的哈希不同(我想知道为什么?)。有人知道Python 3.2中如何实现__hash__
吗?
#Version: Python 3.2
def c_mul(a, b):
#C type multiplication
return eval(hex((int(a) * b) & 0xFFFFFFFF)[:-1])
class hs:
#Python 2.x algorithm for hash from http://effbot.org/zone/python-hash.htm
def __hash__(self):
if not self:
return 0 # empty
value = ord(self[0]) << 7
for char in self:
value = c_mul(1000003, value) ^ ord(char)
value = value ^ len(self)
if value == -1:
value = -2
return value
def main():
s = ["PROBLEM", "PROBLEN", "PROBLEO", "PROBLEP"]#, "PROBLEQ", "PROBLER", "PROBLES"]
print("Python 3.2 hash() bild-in")
for c in s[:]: print("hash('", c, "')=", hex(hash(c)), end="\n")
print("\n")
print("Python 2.x type hash: __hash__()")
for c in s[:]: print("hs.__hash__('", c, "')=", hex(hs.__hash__(c)), end="\n")
if __name__ == "__main__":
main()
OUTPUT:
Python 3.2 hash() bild-in
hash(' PROBLEM ')= 0x7a8e675a
hash(' PROBLEN ')= 0x7a8e6759
hash(' PROBLEO ')= 0x7a8e6758
hash(' PROBLEP ')= 0x7a8e6747
Python 2.x type hash: __hash__()
hs.__hash__(' PROBLEM ')= 0xa638a41
hs.__hash__(' PROBLEN ')= 0xa638a42
hs.__hash__(' PROBLEO ')= 0xa638a43
hs.__hash__(' PROBLEP ')= 0xa638a5c