On Tue, Nov 23, 2021 at 7:47 PM Stephen J. Turnbull <stephenjturnb...@gmail.com> wrote: > > Chris Angelico writes: > > > It's not too hard to create your own dataflow class if you want one. > > It can start with any arbitrary iterable, and then have your map and > > filter methods just the same. > > One thing I noticed when implementing this class (yours is better, so > I'm not posting mine :-) is that you and I both implemented .map in > the obvious way for this use case, but the map function takes multiple > iterables. On the other hand, filter takes only one iterable > argument.
Extending map to more than just one function and one iterable is done in different ways by different languages. I don't think it necessarily needs to be implemented the same way in a pipeline as it is in a stand-alone map function; the pipeline is, by its nature, working with a single iterable, so if its map method took anything more than a single argument, it could just as easily be interpreted as "pass these arguments to the function" (so you could >>iter(x).map(int, 16)<< to convert hex to decimal) rather than as extra iterables. Which is why I kept it simple and didn't allow more args :) > Obviously, you can implement multifilter > > def multifilter(func, *iterables): > filter(lambda x: func(*x), zip(*iterables)) > > I think generalizing to this is a YAGNI, since it's so simple. Agreed, not really a lot of point. > Also, returning an iterable of tuples may not be the right thing. > That is, you might want it to return a tuple of iterables, but that > would be messy to implement, and in general can't be done > space-efficiently I think. This apparently is a "no one ever needed > it." I think you're right there. > There's also implementing zip's strict argument, eg, > > def zippymap(func, *iterables, strict=False): > return map(lambda x: func(*x), zip(*iterables, strict)) > > and corresponding zippymappers for any other mappers (including > filter). This seems like it might be useful extension to the > functions in the stdlib for the same reason that it's useful for zip > itself. Even though it's so easy to implement in terms of zip, it > would be more discoverable as a documented argument to the functions. > > Comments? Given that I don't actually want a pipeline like this, I'm not the best one to ask, but I would strongly favour ultra-simple APIs. ChrisA _______________________________________________ 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/ABWVTWDWSEW6L32DFVXTSXCXM4VXSGKB/ Code of Conduct: http://python.org/psf/codeofconduct/
