Python 中的动态关键字参数？
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Dynamic Keyword Arguments in Python?
提问by user42876
Does python have the ability to create dynamic keywords?
python有能力创建动态关键字吗？
For example:
例如：
qset.filter(min_price__usd__range=(min_price, max_price))
I want to be able to change the usdpart based on a selected currency.
我希望能够根据所选货币更改美元部分。
回答by jfs
Yes, It does. Use **kwargsin a function definition.
是的，它确实。使用**kwargs在函数定义。
Example:
例子：
def f(**kwargs):
print kwargs.keys()
f(a=2, b="b") # -> ['a', 'b']
f(**{'d'+'e': 1}) # -> ['de']
But why do you need that?
但你为什么需要那个？
回答by James Hopkin
If I understand what you're asking correctly,
如果我理解你的要求是正确的，
qset.filter(**{
'min_price_' + selected_currency + '_range' :
(min_price, max_price)})
does what you need.
做你需要的。
回答by Benjamin Pollack
You can easily do this by declaring your function like this:
你可以通过像这样声明你的函数来轻松地做到这一点：
def filter(**kwargs):
your function will now be passed a dictionary called kwargs that contains the keywords and values passed to your function. Note that, syntactically, the word kwargsis meaningless; the **is what causes the dynamic keyword behavior.
您的函数现在将传递一个名为 kwargs 的字典，其中包含传递给您的函数的关键字和值。请注意，从句法上来说，这个词kwargs是没有意义的；这**就是导致动态关键字行为的原因。
You can also do the reverse. If you are calling a function, and you have a dictionary that corresponds to the arguments, you can do
你也可以反过来做。如果你正在调用一个函数，并且你有一个对应于参数的字典，你可以这样做
someFunction(**theDictionary)
There is also the lesser used *foo variant, which causes you to receive an array of arguments. This is similar to normal C vararg arrays.
还有一个较少使用的 *foo 变体，它使您接收一组参数。这类似于普通的 C vararg 数组。
回答by Benjamin Pollack
Yes, sort of. In your filter method you can declare a wildcard variable that collects all the unknown keyword arguments. Your method might look like this:
是的，有点。在您的过滤器方法中，您可以声明一个通配符变量来收集所有未知的 关键字参数。您的方法可能如下所示：
def filter(self, **kwargs):
for key,value in kwargs:
if key.startswith('min_price__') and key.endswith('__range'):
currency = key.replace('min_price__', '').replace('__range','')
rate = self.current_conversion_rates[currency]
self.setCurrencyRange(value[0]*rate, value[1]*rate)
