python - 使用装饰器检查可选参数

Question

我正在尝试弄清楚如何编写装饰器来检查是否使用特定的可选参数调用函数。这可能不是检查参数的 pythonic 方式，但无论如何我都想知道使用装饰器的解决方案。这是我正在寻找的示例:

@require_arguments("N", "p")  # Question here

def g(x,*args,**kwargs):
    if "N" not in kwargs: raise SyntaxError("missing N")
    if "p" not in kwargs: raise SyntaxError("missing p")
    print x

g(3,N=2) # Raise "missing p"

如何编写会引发相应错误的装饰器 @require_arguments(*args)？

Answer 1

给你:

def require_arguments(*reqargs):
    def decorator(func):
        def wrapper(*args, **kwargs):
            for arg in reqargs:
                if not arg in kwargs:
                    raise TypeError("Missing %s" % arg)
            return func(*args, **kwargs)
        return wrapper
    return decorator

@require_arguments("N", "p")  # Question here
def g(x,*args,**kwargs):
    print x

g(3,N=2) # Raise "missing p"

输出:

Traceback (most recent call last):
  File "arg.py", line 19, in <module>
    g(3,N=2) # Raise "missing p"
  File "arg.py", line 7, in wrapper
    raise ValueError("Missing %s" % arg)
ValueError: Missing p