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Then, the gain in terms of memory occupancy and performance. What are the other consequences of adding _slots_? First, the complete disappearance of _dict_: > mon_objet_slotte._dict_ĪttributeError: ‘MaClasseSlottee’ object has no attribute ‘_dict_’ Indeed, the attribute d does not appear in the list of those we have declared. No other will be accepted: > mon_objet_slotte.d = 4ĪttributeError: ‘MaClasseSlottee’ object has no attribute ‘d’ That’s all! Just add an attribute of class _slots_ returning to an iterable with the names of the instance attributes that you want to manipulate.

slots plus

> mon_objet_slotte = MaClasseSlottee(1, 2) Let’s see how to redefine this one with slots. In the previous example, I defined three attributes during the life of my object. Methods that can be applied to it for example, which are class attributes. From theīeginning, I took care to talk about instance attributes to make theĭistinction with the other attributes accessible from an object, like the PresentationĪ way of declaring instance attributes that make up our objects. It is actually mainly for this performance issue that Guido van Rossum created the slots. Having to look for an attribute in a Python dictionary is probably not the most Heuristic that it seems we do not need to know. It is in the obligation toĪllocate memory to the blind, a first time. Implementation of Python and we are interested here. Since they are extensible, their implementationĬannot be optimal with regard to these criteria. It is from this simple observation that I began veryĮarly to ask myself the question of performance and compactness in memory of Of the type self.x, whether in the _init_ method or elsewhere, end in this Indeed, the last line of code is equivalent to: > mon_objet._dict_ = 3Īll the instance attributes added via an instruction How does it work? Without dwelling on the subtleties of access to attributes, it is the existence of a special attribute called _dict_ that makes the operation possible. We see that the interpreter accepts that I added the attribute c. But that does not prevent us from adding on the fly thereafter.

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At best, in the _init_ method of the object we initialize a number of instance attributes. When we write a class in Python, we do not make a static statement of its attributes. Nevertheless, I discovered on this occasion that there was a way to partially solve this problem since the appearance of new classes in Python 3: resort to attribute declarations called slots.

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Optimal in most cases, resulting from the choice of original designs that were It quickly became clear to me that this was not As a former C developer working in high-performanceĬomputing, I wondered very early about the compactness of objects that wereĬommonly created in Python.















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