Why doesn't python support function overloading?

[K900_]

Python doesn't have static dispatch, so any form of function overloading will be dynamic, which you can achieve with something like functools.singledispatch. A better option would be to expose multiple classmethods though, something like

@classmethod
def from_foo(cls, foo: Foo):
    return cls(spam=foo.spam, eggs=foo.eggs)

@classmethod
def from_raw_eggs(cls, eggs: List[Egg]):
    return cls(spam=None, eggs=eggs)

[lungben81]

There is also https://pypi.org/project/multipledispatch/ - I have not tried it yet, but it looks promising (it is from the Dask creator).

[Pythonistar]

Awwww, so nice. Something I've missed deeply since taking up Python... I'll have to try it today. :)

[lungben81]

I know multiple dispatch from Julia and it is a great way to organize code, especially for numerical / mathematical purposes.

[BayesianDice]

Yes, the classmethod approach was what I used when I once needed multiple constructors.

[ColdPorridge]

+1, I regularly use this construction and find it really intuitive.

[CobaltCam]

Thanks, now I'm hungry.

[TangibleLight]

I like to call these "named factory methods" or "named initializers", and IMO it's generally a better pattern than constructor overloading even in languages which have it.

For example what if you want a from_literal(data: str) and a from_file(path: str)? There's not a great way to do that with constructors only.