在使用 lru_cache 装饰器时将不同的参数模式视为相同的调用

Question

如 official documentation 中所述，Python 的 functools.lru_cache 装饰器将不同的参数模式解释为完全不同的缓存键。例如：

import functools

@functools.lru_cache(maxsize=128)
def test(a, b, *, c, d):
    print(f'Hello from function: ({a}, {b}, {c}, {d})')

test(1, 2, c=42, d='answer')
test(1, 2, d='answer', c=42)
test(b=2, a=1, c=42, d='answer')

虽然实际上所有函数调用都是相同的，但上面的代码会产生以下输出：

Hello from function: (1, 2, 42, answer)
Hello from function: (1, 2, 42, answer)
Hello from function: (1, 2, 42, answer)

什么是更“pythonic”的方法来克服将此类调用视为相同的问题？

Answer 1

我对python不太熟悉，我能想到的方法是添加另一个装饰器来对传递给lru_cache的参数进行排序。

#!/usr/bin/env python3

from functools import update_wrapper, lru_cache
import inspect

def sorted_params(func):
    sig = inspect.signature(func, follow_wrapped=True)
    def wrapper(*args, **kwargs):
        b = sig.bind(*args, **kwargs)
        return func(*b.args, **b.kwargs)
    return update_wrapper(wrapper, func)

@lru_cache
def test1(a, b, *, c, d):
    print(f'Hello from test1: ({a}, {b}, {c}, {d})')

@sorted_params
@lru_cache
def test2(a, b, *, c, d):
    print(f'Hello from test2: ({a}, {b}, {c}, {d})')

for func in [test1, test2]:
    print('-'*30)
    func(1, 2, c=42, d='answer')
    func(1, 2, d='answer', c=42)
    func(b=2, a=1, c=42, d='answer')

输出：

------------------------------
Hello from test1: (1, 2, 42, answer)
Hello from test1: (1, 2, 42, answer)
Hello from test1: (1, 2, 42, answer)
------------------------------
Hello from test2: (1, 2, 42, answer)

Answer 2

在另一个装饰器中使用 inspect.signature 规范化参数模式：

import functools
import inspect

def normalize_arg_patterns(func):
    sig = inspect.signature(func)
    @functools.wraps(func)
    def _func(*args, **kwargs):
        ba = sig.bind(*args, **kwargs)
        args, kwargs = ba.args, ba.kwargs
        return func(*args, **kwargs)
    return _func

用法：

@normalize_arg_patterns  # Add this
@functools.lru_cache(maxsize=128)
def test(a, b, *, c, d):
    print(f'Hello from function: ({a}, {b}, {c}, {d})')

test(1, 2, c=42, d='answer')
test(1, 2, d='answer', c=42)
test(b=2, a=1, c=42, d='answer')

Python 3.2 和 2.7

在另一个装饰器中使用 inspect.getcallargs 规范化参数模式：

import functools
import inspect

def normalize_arg_patterns(func):
    f = inspect.unwrap(func)
    @functools.wraps(func)
    def _func(*args, **kwargs):
        args, kwargs = (), inspect.getcallargs(f, *args, **kwargs)
        kwargs = dict(sorted(kwargs.items()))
        return func(*args, **kwargs)
    return _func

在使用 lru_cache 装饰器时将不同的参数模式视为相同的调用

Treat distinct argument patterns while using lru_cache decorator as the same calls

python

functools

Python 3.2 和 2.7