Does python have magic methods for all it's built-in functions?

Question

Python supports a lot of magic methods for implementing custom functionality in objects, such as __lt__, __getattr__, etc. There are even magic methods that affect the way certain built-in functions perform, such as __len__ and __instancecheck__. But are there magic methods for all the built-in functions in python?

For example, if I wanted to change the way the any function would perform on a certain class, could I specify an __any__ magic method in that class? If that isn't an option, is there any way that I could specifically affect the way any applies to that class? (I realize that if I wanted special functionality for the way any receives the items from the iterable I could define __iter__, but that's not what I am looking to do)

Note that my desire to implement custom functionality for any is just an example, I don't explicitly want to define custom functionality for any.

No, there are plenty of built-in functions where hooking makes no sense. chr() for example, or id(). — Martijn Pieters
– Martijn Pieters, Commented Feb 15, 2014 at 18:34
@MartijnPieters, It makes a decent bit of sense for chr, if you were making your own number type you wanted to be used wherever an int can be used. — Mike Graham
– Mike Graham, Commented Feb 15, 2014 at 18:45
@MikeGraham Actually, that can be done by defining __int__, which is much more appropriate for that purpose. — user395760
– user395760, Commented Feb 15, 2014 at 19:19

Martijn Pieters · Accepted Answer · 2014-02-15 18:43:46Z

4

The special method's let you hook into concepts, not so much built-in functions or other things.

__len__ is a container length, not specifically a hook for the len() function. It just happens that the len() function is the visible API for that functionality.

any() expects an iterable argument, the concept you are looking for here is the Iterator type methods; it's not the function that is hooked, it is that concept.

You may want to study the default type abstract base classes to see what methods Python types implement; here many special methods are grouped together in a readable overview.

edited Feb 15, 2014 at 18:43

answered Feb 15, 2014 at 18:37

Martijn Pieters

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2 Comments

Mike Graham Over a year ago

"any() expects an *iterator argument" No, any expects an iterable argument.

Martijn Pieters Over a year ago

@MikeGraham: indeed, iter() is called on it, so a iterable is enough. For some reason I still use the terms interchangeable but there is a difference that I should pay attention to more..

Mike Graham · Accepted Answer · 2014-02-15 18:40:17Z

1

No, only for lots of them, as practicality demands.

(Specifically for __any__, it has been discussed before, but ultimately, it wasn't considered to be needed.)

answered Feb 15, 2014 at 18:40

Mike Graham

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Brian Neal · Accepted Answer · 2014-02-15 18:37:00Z

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No. The list of special methods a class can implement are documented in section 3.3.

answered Feb 15, 2014 at 18:37

Brian Neal

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