functools.lru_cache 具有相同哈希值的两个对象之间的差异

Question

阅读 https://github.com/python/cpython/blob/master/Lib/functools.py 的代码后，我认为 lru_cache 使用散列从函数参数构建一个键，所以如果我的两个对象具有相同的 hash 它们应该是lru_cache.

也一样

如果您运行此代码：

from functools import lru_cache

COUNT=0
@lru_cache(maxsize=None)
def fnc(*args, **kvargs):
    global COUNT
    COUNT=COUNT+1
    return COUNT, hash(args[0]), args ,kvargs

class MyClass:
    def __init__(self, *args, **kvargs):
        self._init_args=(args, frozenset(kvargs.items()))
    def __hash__(self):
        return hash(self._init_args)

m1a = MyClass(1)
m2a = MyClass(2)
m1b = MyClass(1)
m2b = MyClass(2)
fnc(m1a) # Output: (1, -7270110455953140331, (<__main__.MyClass object at 0x7fb14b540710>,), {})
fnc(m1a) # Output: (1, -7270110455953140331, (<__main__.MyClass object at 0x7fb14b540710>,), {})
fnc(m2a) # Output: (2, 7567087542259278010, (<__main__.MyClass object at 0x7fb14b540810>,), {})
fnc(m2a) # Output: (2, 7567087542259278010, (<__main__.MyClass object at 0x7fb14b540810>,), {})
fnc(m1b) # Output: (3, -7270110455953140331, (<__main__.MyClass object at 0x7fb14b540610>,), {})
fnc(m2b) # Output: (4, 7567087542259278010, (<__main__.MyClass object at 0x7fb14b540b50>,), {})

你可以看到 lru_cache 正在检测 m1a 和 m1b 不同，即使它们具有相同的 hash。

我该怎么做才能使 lru_cache 不区分具有相同 __init__ 个参数的两个 MyClass 实例？

Answer 1

lru_cache 首先使用 __hash__ 然后检查 __eq__
将 __eq__ 方法添加到您的 class

    def __eq__(self, other):
        return type(self) == type(other) and self._init_args == other._init_args

functools.lru_cache 具有相同哈希值的两个对象之间的差异

functools.lru_cache difference between two object with same hash

python

hash

caching

functools