你如何在 Python 中调用类的实例？
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How do you call an instance of a class in Python?
提问by Aaron Hall
This is inspired by a question I just saw, "Change what is returned by calling class instance", but was quickly answered with __repr__(and accepted, so the questioner did not actually intend to call the instance).
这是受到我刚刚看到的一个问题的启发，“通过调用类实例更改返回的内容”，但很快得到了回答__repr__（并被接受，因此提问者实际上并不打算调用该实例）。
Now calling an instance of a class can be done like this:
现在可以像这样调用一个类的实例：
instance_of_object = object()
instance_of_object()
but we'll get an error, something like TypeError: 'object' object is not callable.
但是我们会得到一个错误，比如TypeError: 'object' object is not callable.
This behavior is defined in the CPython source here.
So to ensure we have this question on Stackoverflow:
所以为了确保我们在 Stackoverflow 上有这个问题：
How do you actually call an instance of a class in Python?
你实际上如何在 Python 中调用类的实例？
采纳答案by Aaron Hall
You call an instance of a class as in the following:
您可以调用类的实例，如下所示：
o = object() # create our instance
o() # call the instance
But this will typically give us an error.
但这通常会给我们一个错误。
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'object' object is not callable
How can we call the instance as intended, and perhaps get something useful out of it?
我们如何按预期调用实例，并从中获取有用的信息？
We have to implement Python special method, __call__!
我们必须实现 Python 的特殊方法，__call__！
class Knight(object):
def __call__(self, foo, bar, baz=None):
print(foo)
print(bar)
print(bar)
print(bar)
print(baz)
Instantiate the class:
实例化类：
a_knight = Knight()
Now we can call the class instance:
现在我们可以调用类实例：
a_knight('ni!', 'ichi', 'pitang-zoom-boing!')
which prints:
打印：
ni!
ichi
ichi
ichi
pitang-zoom-boing!
And we have now actually, and successfully, calledan instance of the class!
我们现在实际上并成功地调用了类的一个实例！
