On Wed, Mar 7, 2018 at 2:12 AM, Kirill Balunov <kirillbalu...@gmail.com> wrote: > > > 2018-03-06 17:55 GMT+03:00 Chris Angelico <ros...@gmail.com>: >> >> On Wed, Mar 7, 2018 at 1:48 AM, Kirill Balunov <kirillbalu...@gmail.com> >> wrote: >> > Note: For some historical reasons as the first argument you can use None >> > instead of function, in this case the identity function is assumed. That >> > is, all elements of iterable that are false are removed which is >> > equivalent >> > to (item for item in iterable if item). Currently, for the same purpose >> > the >> > preferred form is `filter(bool, iterable)`. >> > >> >> I'd prefer to word it something like: >> >> If the first argument is None, the identity function is assumed. That >> is, all elements of the iterable that are false are removed; it is >> equivalent to (item for item in iterable if item). It is approximately >> equivalent to (but faster than) filter(bool, iterable). >> >> ChrisA >> -- >> https://mail.python.org/mailman/listinfo/python-list > > > I do not want to seem rude and stubborn, but how much faster is it to > highlight or emphasize it: >
Timings mean little. Why do we write: if lst: instead of: if bool(lst): ? Because it's unnecessary and pointless to call bool() on something before using it in a boolean context. If that concept causes you problems, it's not the fault of the filter function; filter simply uses something in a boolean context. So "the identity function" is more correct than "the bool() function". ChrisA -- https://mail.python.org/mailman/listinfo/python-list
