Support functools.partial for event handlers

[wwwillchen]

Fixes #766

[malmaud]

I'm not a super-expert on the best way to do this but this seems reasonable to me.

[wwwillchen]

@richard-to WDYT about this feature / implementation? I think the feature is useful, but the implementation is a little bit hairy. In particular, we need to avoid getting a repr for types that return a memory address (e.g. vanilla Python classes)

class Car:
  def __init__(self, name: str) -> None:
    self.name = name

car = Car(name="a") # repr -> <__main__.Car object at 0x79cfdc146080>

[richard-to]

Nice! I remember when I first started using Mesop, I had tried using functools.partial to no avail.

Looking at the code example, it does make the devex a lot nicer than having to pass in a key and then parsing the string.

Question: does this work when doing a dynamic loop? Say I wanted to add an event handler to each box using partial?

Yes, the limitation of needing a stable repr is interesting. How much of a drawback do you think that will be in practice? I think it may be slightly annoying, but the improvement in devex is worth it I think (granted I haven't tested this out with some of the uses I have for this yet)

[wwwillchen]

Nice! I remember when I first started using Mesop, I had tried using functools.partial to no avail.

Looking at the code example, it does make the devex a lot nicer than having to pass in a key and then parsing the string.

Question: does this work when doing a dynamic loop? Say I wanted to add an event handler to each box using partial?

Yup. I added an example in the functools_partial example.

Yes, the limitation of needing a stable repr is interesting. How much of a drawback do you think that will be in practice? I think it may be slightly annoying, but the improvement in devex is worth it I think (granted I haven't tested this out with some of the uses I have for this yet)

I think it's not too bad since this should cover most of the cases. It may be a little hard to understand for Mesop app developers, but I think we can work on improving the error message + docs if this becomes a common issue.

Thanks for the feedback, I'll merge this in.