On Tue, Dec 10, 2019 at 07:21:13PM -0600, Tim Peters wrote:
[Tim]
For me, most of the time, it's to have an obvious, uniform way to spell "non-destructively pick an object from a container (set, dict, list, deque, heap, tuple, custom tree class, ...)". I don't even have iterators in mind then, except as an implementation detail.
[Steven]
You can't *non-destructively* pick the first (or next, or any) element of an iterator.
Obviously. That's why I wrote "container", and then gave 7 concrete examples in case that distinction was too subtle ;-)
It wasn't :-) but we're talking about adding a function to **itertools** not "container tools", one which will behave subtly different with containers and iterators. Your use-case ("first item in a container") is not the same as the semantics "next element of an iterator", even if we call the second one "first". [...]
I'm not at all bothered that for some arguments `first()` mutates state and for others it doesn't, no more than I'm bothered that `for x in iterable:` may or may not "consume" the iterable.
*shrug* Okay, but I am. Iterating over an iterable is a very different use-case. [...]
While the meaning of `first()` is clear for any iterable argument.
Sorry Tim, I have to disagree. The meaning of `first` is: return the first element of a sequence or container (in standard iteration order), OR the *next* element of an iterator and I don't think that this is even a little bit clear from the name. -- Steven