Question

我需要能够在一个接受基于字符串名称和变量字典的各种参数的类上动态调用方法。我知道如何使用inspect模块找到签名，我可以使用getattr获取方法，但我不知道如何以正确的顺序分配参数以纯粹动态的方式调用它。

class MyClass():
    def call_me(a, b, *args, foo='bar', **kwargs):
        print('Hey, I got called!')

command = {
          'action':'call_me',
          'parameters':{
                        'a': 'Apple',
                        'b': 'Banana',
                        'args':['one','two','three','four'],
                        'foo':'spam',
                        'clowns':'bad',
                        'chickens':'good'
                       }
           }

me = MyClass()
action = getattr(me,command['action'])

... now what?

我需要能够像使用此代码一样动态调用此函数，而无需预先知道该方法的实际参数：

a = command['parameters']['a']
b = command['parameters']['b']
args = command['parameters']['args']
foo = command['parameters']['foo']
kwargs = {
          'clowns': command['parameters']['clowns'],
          'chickens':command['parameters']['chickens']
         }

value = action(a, b, *args, foo=foo, **kwargs)

肯定有一种很好的pythonic方法可以做到这一点。

编辑：修复getattr直接调用MyClass实例而不是MyClass。

Answer 1

这是迄今为止我发现的最好的方法，可以捕获普通args，* args，关键字args和** kwargs的所有组合而不会出现任何错误：

import inspect
class MyClass():
    def a(self):
        pass
    def b(self,foo):
        pass
    def c(self,foo,*extras):
        pass
    def d(self,foo,food='spam'):
        pass
    def e(self,foo,**kwargs):
        pass
    def f(self,foo,*extras,food='spam'):
        pass
    def g(self,foo,*extras,**kwargs):
        pass
    def h(self,foo,*extras,food='spam',**kwargs):
        pass
    def i(self,*extras):
        pass
    def j(self,*extras,food='spam'):
        pass
    def k(self,*extras,**kwargs):
        pass
    def l(self,*extras,food='spam',**kwargs):
        pass
    def m(self,food='spam'):
        pass
    def n(self,food='spam',**kwargs):
        pass
    def o(self,**kwargs):
        pass


def dynamic_invoke(obj,name,parameters):
    action = getattr(obj,name)
    spec = inspect.getfullargspec(action)

    used = []
    args = ()
    kwargs = {}

    for a in spec.args[1:]:
        # skip the "self" argument since we are bound to a class
        args += (parameters[a], )
        used.append(a)

    if spec.varargs:
        args += tuple(parameters[spec.varargs])
        used.append(spec.varargs)

    for kw in spec.kwonlyargs:
        try:
            kwargs[kw] = parameters[kw]
            used.append(kw)
        except KeyError:
            pass

    # pass remaining parameters to kwargs, if allowed
    if spec.varkw:
        for k,v in parameters.items():
            if k not in used:
                kwargs[k] = v

    return action(*args,**kwargs)

me = MyClass()
params = {
        'foo':'bar',
        'extras':['one','two','three','four'],
        'food':'eggs',
        'parrot':'blue'
        }

dynamic_invoke(me,'a',params)
dynamic_invoke(me,'b',params)
dynamic_invoke(me,'c',params)
dynamic_invoke(me,'d',params)
dynamic_invoke(me,'e',params)
dynamic_invoke(me,'f',params)
dynamic_invoke(me,'g',params)
dynamic_invoke(me,'h',params)
dynamic_invoke(me,'i',params)
dynamic_invoke(me,'j',params)
dynamic_invoke(me,'k',params)
dynamic_invoke(me,'l',params)
dynamic_invoke(me,'m',params)
dynamic_invoke(me,'n',params)
dynamic_invoke(me,'o',params)
print('done!')

Answer 2

试试这样：

action = getattr(me,command['action'])
action(**{'a': 'Apple',
      'b': 'Banana',
      'args':['one','two','three','four'],
      'foo':'spam',
      'clowns':'bad',
      'chickens':'good'
     })

Python3：使用参数字典动态调用方法

2 个答案: