多变量声明 [英] Multiple variable declaration

问题描述

我在Python中看到了这个声明，但是我不明白这意味着什么，也找不到解释:

I saw this declaration in Python, but I don't understand what it means and can't find an explanation:

ret, thresh = cv2.threshold(imgray, 127, 255, 0)

问题是:为什么ret和thresh之间会有逗号?那是什么类型的作业?

The question is: why is there there a comma between ret and thresh? What type of assignment is that?

推荐答案

这是一个元组" 或解构" 作业-参见例如多种分配语义. cv2.threshold返回一个包含两个值的元组，因此等效于:

That's a "tuple" or "destructuring" assignment - see e.g. Multiple assignment semantics. cv2.threshold returns a tuple containing two values, so it's equivalent to:

temp = cv2.threshold(...)
ret = temp[0]
thresh = temp[1]

请参见语言参考中的赋值声明:

如果目标列表是目标的逗号分隔列表:该对象必须是可迭代的，并且具有与目标列表中存在目标的项目数量相同的项目，并且将这些项目从左到右分配给相应的目标.

If the target list is a comma-separated list of targets: The object must be an iterable with the same number of items as there are targets in the target list, and the items are assigned, from left to right, to the corresponding targets.

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