Python decorator to raise a RuntimeError if any of the arguments are None when called

raise_on_none.py

import inspect
def raise_on_none(f):
    arg_spec = inspect.getargspec(f)
    def new_f(*args, **kwargs):
        bound_args = inspect.getcallargs(f, *args, **kwargs)
        if(any([bound_args[a]==None for a in arg_spec.args])):
            raise RuntimeError('Named arg is None')
        if(arg_spec.keywords != None):
            if(any([a==None for a in bound_args[arg_spec.keywords].values()])):
                raise RuntimeError('Keyword arg is None')
        if(arg_spec.varargs != None):
            if(any([a==None for a in bound_args[arg_spec.varargs]])):
                raise RuntimeError('Var arg is None')
        return f(*args, **kwargs)
    new_f.spec = arg_spec
    return new_f
    
# Example
@raise_on_none
def fn_x(a,b,c,d=None,e=None):
    print a,b,c,d,e
    
fn_x(1,2,3,4)
# -> RuntimeError: Named arg is None