Python3.8环境下如何为装饰器添加传入函数的签名类型校验

你可以直接使用Python标准库的inspect和typing.get_type_hints实现需求，无需第三方依赖，完全适配Python3.8版本。校验逻辑会在装饰器执行阶段（也就是你打印decorating function...的阶段）直接执行，不通过就抛出明确报错，不会等到函数运行时才校验。

完整实现代码 #

from dataclasses import dataclass
from typing import Callable, get_type_hints
from inspect import signature

@dataclass
class User:
    name: str

@dataclass
class Point:
    x: float
    y: float
    z: float

def logging_decorator(f: Callable[[User, Point], bool]) -> Callable[[User, Point], bool]:
    # 签名校验逻辑
    sig = signature(f)
    param_count = len(sig.parameters)
    # 校验参数数量
    if param_count != 2:
        raise ValueError(f"签名不符合要求：期望2个参数，实际传入{param_count}个参数")
    
    hints = get_type_hints(f)
    # 校验返回值类型
    if 'return' not in hints:
        raise ValueError("签名不符合要求：缺少返回值类型注解，期望返回bool")
    if hints['return'] is not bool:
        raise ValueError(f"签名不符合要求：返回值类型期望bool，实际得到{hints['return'].__name__}")
    
    # 按顺序校验两个参数的类型
    expected_types = [User, Point]
    param_names = list(sig.parameters.keys())
    for idx in range(2):
        param_name = param_names[idx]
        expected_type = expected_types[idx]
        if param_name not in hints:
            raise ValueError(f"签名不符合要求：第{idx+1}个参数[{param_name}]缺少类型注解，期望{expected_type.__name__}")
        actual_type = hints[param_name]
        if actual_type is not expected_type:
            raise ValueError(f"签名不符合要求：第{idx+1}个参数[{param_name}]类型期望{expected_type.__name__}，实际得到{actual_type.__name__}")
    
    # 原有逻辑
    print('decorating function...')
    def decorated(a: User, b: Point) -> bool:
        print(f'User {a.name} calling with points {b.x},{b.y},{b.z}')
        ret = f(a, b)
        print(f'returned {ret}')
        return ret
    return decorated

测试效果 #

# 正常装饰，无报错
@logging_decorator
def good_f(a: User, b: Point) -> bool:
    return True

# 装饰阶段直接抛出错误：ValueError: 签名不符合要求：返回值类型期望bool，实际得到str
@logging_decorator
def bad_f(a: str, b: str) -> str:
    return "Hello"

内容的提问来源于stack exchange，提问作者Blue7