Understanding __get__ and __set__ and Python descriptors -

I'm trying to understand what Python descriptors are and for that How useful can be However, I am failing it. I understand how they work, but this is my suspicion. Consider the following code:

  square celsius (object): def __init __ (self, value = 0.0): self.value = float (value) def __get __ (self, example, owner ): Return Self.value def __set __ (self, example, value): self.value = float (value) square temperature (object): Celsius = Celsius ()  

1. Why do I need a descriptor class? Please use this example or what you think is better.

2. What is the example and owner here? (In __ go __ ). So my question is, what is the purpose of the third parameter here?

3. How do I call / use this example?

The descriptor is how the property of Python Type is applied, a descriptor just applies __ , __ set __ , etc. and then its definition is added to the second category (as You did the temperature above the class). For example:

  temporary = temperature () temp.celsius #calls.calca___get__  

To access the property that you have given to the teller ( is assigned to Celsius) in the above example) calls the appropriate descriptor method. Example of __ go __ class in the

example (above, code> __ go __ will receive temp , while owner is square with pigment (hence it will be temperature ).

You need to understand the reasoning of using a descriptor class In this way, if a descriptor is used to cache some expensive operations, then it can store the value automatically and It can not be classed.

An article about a descriptor can be edited

As jchl said in the comment, if you simply Temperature.celsius , example will be none .