你能列出函数接收的关键字参数吗? [英] Can you list the keyword arguments a function receives?

问题描述

我有一个字典，我需要将键/值作为关键字参数传递.. 例如..

d_args = {'kw1': 'value1', 'kw2': 'value2'}示例(** d_args)

这很好用，但是如果 d_args dict 中有不被 example 函数接受的值，它显然会死.说，如果 example 函数定义为 def example(kw2):

这是一个问题，因为我不控制 d_args 或 example 函数的生成.它们都来自外部模块，而 example 只接受字典中的一些关键字参数..

理想情况下我会这样做

parsed_kwargs = feedparser.parse(the_url)valid_kwargs = get_valid_kwargs(parsed_kwargs，valid_for = PyRSS2Gen.RSS2)PyRSS2Gen.RSS2(**valid_kwargs)

我可能只是从有效关键字参数列表中过滤字典，但我想知道:有没有办法以编程方式列出特定函数采用的关键字参数?>

解决方案

比直接检查代码对象并计算变量更好一点的是使用检查模块.

<预><代码>>>>进口检验>>>def func(a,b,c=42, *args, **kwargs): 通过>>>检查.getargspec(函数)(['a', 'b', 'c'], 'args', 'kwargs', (42,))

如果你想知道它是否可以用一组特定的参数调用，你需要没有指定默认值的参数.这些可以通过以下方式获得:

def getRequiredArgs(func):args, varargs, varkw, defaults = inspect.getargspec(func)如果默认:args = args[:-len(defaults)]return args # *args 和 **kwargs 不是必需的，所以忽略它们.

然后有一个函数可以告诉您在特定的 dict 中缺少什么:

def missingArgs(func, argdict):返回集(getRequiredArgs(func)).difference(argdict)

同样，要检查无效参数，请使用:

def invalidArgs(func, argdict):args, varargs, varkw, defaults = inspect.getargspec(func)if varkw: return set() # 全部接受返回集(argdict) - 集(args)

所以一个完整的测试是否可以调用是:

def isCallableWithArgs(func, argdict):返回 not missingArgs(func, argdict) 和 not invalidArgs(func, argdict)

(这仅适用于 python 的 arg 解析.显然无法检测到任何运行时检查 kwargs 中的无效值.)

I have a dict, which I need to pass key/values as keyword arguments.. For example..

d_args = {'kw1': 'value1', 'kw2': 'value2'}
example(**d_args)

This works fine, but if there are values in the d_args dict that are not accepted by the example function, it obviously dies.. Say, if the example function is defined as def example(kw2):

This is a problem since I don't control either the generation of the d_args, or the example function.. They both come from external modules, and example only accepts some of the keyword-arguments from the dict..

Ideally I would just do

parsed_kwargs = feedparser.parse(the_url)
valid_kwargs = get_valid_kwargs(parsed_kwargs, valid_for = PyRSS2Gen.RSS2)
PyRSS2Gen.RSS2(**valid_kwargs)

I will probably just filter the dict, from a list of valid keyword-arguments, but I was wondering: Is there a way to programatically list the keyword arguments the a specific function takes?

解决方案

A little nicer than inspecting the code object directly and working out the variables is to use the inspect module.

>>> import inspect
>>> def func(a,b,c=42, *args, **kwargs): pass
>>> inspect.getargspec(func)
(['a', 'b', 'c'], 'args', 'kwargs', (42,))

If you want to know if its callable with a particular set of args, you need the args without a default already specified. These can be got by:

def getRequiredArgs(func):
    args, varargs, varkw, defaults = inspect.getargspec(func)
    if defaults:
        args = args[:-len(defaults)]
    return args   # *args and **kwargs are not required, so ignore them.

Then a function to tell what you are missing from your particular dict is:

def missingArgs(func, argdict):
    return set(getRequiredArgs(func)).difference(argdict)

Similarly, to check for invalid args, use:

def invalidArgs(func, argdict):
    args, varargs, varkw, defaults = inspect.getargspec(func)
    if varkw: return set()  # All accepted
    return set(argdict) - set(args)

And so a full test if it is callable is :

def isCallableWithArgs(func, argdict):
    return not missingArgs(func, argdict) and not invalidArgs(func, argdict)

(This is good only as far as python's arg parsing. Any runtime checks for invalid values in kwargs obviously can't be detected.)

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