如何使用 Python 装饰器检查函数参数? [英] How to use Python decorators to check function arguments?

问题描述

我想定义一些通用装饰器来在调用一些函数之前检查参数.

I would like to define some generic decorators to check arguments before calling some functions.

类似于:

@checkArguments(types = ['int', 'float'])
def myFunction(thisVarIsAnInt, thisVarIsAFloat)
    ''' Here my code '''
    pass

附注:

1. 类型检查只是为了展示一个例子
2. 我使用的是 Python 2.7，但 Python 3.0 也应该很有趣

推荐答案

来自 Decorators对于函数和方法:

Python 2

def accepts(*types):
    def check_accepts(f):
        assert len(types) == f.func_code.co_argcount
        def new_f(*args, **kwds):
            for (a, t) in zip(args, types):
                assert isinstance(a, t), \
                       "arg %r does not match %s" % (a,t)
            return f(*args, **kwds)
        new_f.func_name = f.func_name
        return new_f
    return check_accepts

Python 3

在 Python 3 中 func_code 已更改为 __code__ 并且 func_name 已更改为 __name__.

In Python 3 func_code has changed to __code__ and func_name has changed to __name__.

def accepts(*types):
    def check_accepts(f):
        assert len(types) == f.__code__.co_argcount
        def new_f(*args, **kwds):
            for (a, t) in zip(args, types):
                assert isinstance(a, t), \
                       "arg %r does not match %s" % (a,t)
            return f(*args, **kwds)
        new_f.__name__ = f.__name__
        return new_f
    return check_accepts

用法:

@accepts(int, (int,float))
def func(arg1, arg2):
    return arg1 * arg2

func(3, 2) # -> 6
func('3', 2) # -> AssertionError: arg '3' does not match <type 'int'>

arg2 可以是 int 或 float

arg2 can be either int or float

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