On Thu, Sep 29, 2016 at 6:45 PM, Jussi Piitulainen <jussi.piitulai...@helsinki.fi> wrote: > What do you say about things like iterators and generators? I'd say they > are containers, but they count as true even when they are empty. > > bool(x for x in [3,1] if x in [2,7]) # True > list(x for x in [3,1] if x in [2,7]) # [] > > I think the abstraction really leaks on these things.
The problem is that there is no safe way to probe an iterator for emptiness other than to attempt to consume a value from it. How do you know if you're at the EOF of stdin? You ask the user to enter something, and see if s/he presses Ctrl-D (or Ctrl-Z). Until you wait on the user, EOF hasn't necessarily even happened yet. An iterator is not a container, but in many contexts, it can be treated as one. Truthiness is simply not one of those contexts, for reasons of extreme impracticality. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
