On Jul 26, 2019, at 15:05, Kyle Stanley <aeros...@gmail.com> wrote: > > Andrew Barnert wrote: >> consume(print(item) for item in lst) > > From my understanding, consume() effectively provides the functionality the > author was looking for.
Exactly. And it’s readable and concise, and there’s even an implementation in the docs if you don’t think of it yourself. > Also, between the options of `for _ in iter:` vs > `colllections.deque(it, maxlen=0)`, how significant is the performance > difference? > > I had assumed that the performance of `for _ in iter` would be significantly > better, since due to the overhead cost of creating and filling a double ended > queue, > which provides optimization for insertion at the beginning and end. Wouldn't > a one > directional iterator provide better performance and have a lower memory cost > if > there is no modification required? The maxlen of 0 means after determining that 0+1 > 0, the (C) function returns without even getting to the array manipulation stuff. Consuming the iterator in a for loop does even less work inside the loop, but it means the loop is in Python rather than C, which is a lot more expensive than the INC and JNZ that you save. You’re right that it probably rarely makes a difference, but for something that’s going to be recommended in the official docs and potentially used in who-knows-what code, apparently someone thought it was worth the effort to benchmark. I don’t know if anyone has retested this recently, but there was a StackOverflow question maybe 5 years back asking why itertools did this instead of something faster, and IIRC, after testing every idea everyone had an a variety of platforms and versions, the conclusion was that deque was (still) by far the fastest way to do it in CPython (short of a custom C function for consume, and even that isn’t much faster), and not quite the fastest but close enough in PyPy. _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/VPQASVOAH7VHZFXHMEYS4IECDL7AEJKR/ Code of Conduct: http://python.org/psf/codeofconduct/
