Adding new attribute to Poset

[pong]

For convenient, I would like to add an attribute, upper_bounds, to Poset objects

However, after writing the method and issue

Poset.upper_bounds = upper_bounds

X.upper_bounds(S) complains

'FinitePoset_with_category' object has no attribute 'upper_bounds'

When I try

FinitePoset_with_category.upper_bounds = upper_bounds

I got

name 'FinitePoset_with_category' is not defined

So how can one add an attribute to FinitePoset_with_category?

[Eric Gourgoulhon]

Poset is a function, which constructs a finite poset, not the poset class, as you can check:

sage: type(Poset)
<class 'function'>

You can also check it by having a look at the source code:

sage: Poset??

So when you write

Poset.upper_bounds = upper_bounds

you are attaching upper_bounds to the function, not to the class of posets. The latter is FinitePoset (actually a subclass of it, name FinitePoset_with_category, which is constructed dynamically via Sage category mechanism). So you should do

sage: from sage.combinat.posets.posets import FinitePoset

sage: FinitePoset.upper_bounds = upper_bounds

Then

sage: X = Poset(...)

sage: X.upper_bounds(...)

shoud work.

[pong]

Thanks Eric. It works!

I figured out the FinitePoset part after reading the manual. But I know test that it works for X = FinitePoset(...)

I didn't think of trying it with X = Poset(...).