This example uses memoization, basically storing values in a table (dictionary in this case) so you can look them up later instead of recalculating them. Here we use a simple class with a __call__ method to calculate factorials (through a callable object) instead of a factorial function that contains a static variable (as that’s not … Read more
I have been exactly in your case in the past. And I went for magic methods. This was a mistake, the last part of your question says it all : this is slower (than getters/setters) there is no auto-completion (and this is a major problem actually), and type management by the IDE for refactoring and … Read more
AFAIK, len is special in this respect and has historical roots. Here’s a quote from the FAQ: Why does Python use methods for some functionality (e.g. list.index()) but functions for other (e.g. len(list))? The major reason is history. Functions were used for those operations that were generic for a group of types and which were … Read more
First of all A.__dict__.__dict__ is different from A.__dict__[‘__dict__’]. The former doesn’t exist and the latter is the __dict__ attribute that the instances of the class would have. It’s a data descriptor object that returns the internal dictionary of attributes for the specific instance. In short, the __dict__ attribute of an object can’t be stored in … Read more
__get, __set, __call and __callStatic are invoked when the method or property is inaccessible. Your $bar is public and therefor not inaccessible. See the section on Property Overloading in the manual: __set() is run when writing data to inaccessible properties. __get() is utilized for reading data from inaccessible properties. The magic methods are not substitutes … Read more
The way you describe it is absolutely not possible. Assignment to a name is a fundamental feature of Python and no hooks have been provided to change its behavior. However, assignment to a member in a class instance can be controlled as you want, by overriding .__setattr__(). class MyClass(object): def __init__(self, x): self.x = x … Read more
Alex summarized well but, surprisingly, was too succinct. First, let me reiterate the main points in Alex’s post: The default implementation is useless (it’s hard to think of one which wouldn’t be, but yeah) __repr__ goal is to be unambiguous __str__ goal is to be readable Container’s __str__ uses contained objects’ __repr__ Default implementation is … Read more