Search code examples
pythonapimonadsany

Why don't Python's any/all return the found objects?

The Python and and or operators, return values, rather than True or False, which is useful for things such as:

x = d.get(1) or d.get(2) or d.get(3)

Which will make x the value of d[1], d[2] or d[3] which ever is present. This is a bit like having an additive Maybe monad in functional languages.

I've always wanted that the python any() function would be more like a repeated or. I think it would make sense return the object it finds, like:

any([None, None, 1, 2, None]) == 1
any(notnull_iterator) = try: return next(notnull_iterator); except: return None

And likewise for all(). It seems to me the change would be entirely backwards compatible, and increase consistency across the API.

Does anyone know of a previous discussion of this topic?

Solution

  • I guess you're looking for

    first = lambda s: next((x for x in s if x), None)

    e.g. 

    first([None, None,1, 2,None]) # 1

    The "why" question is answered over here.