On Sun, Oct 24, 2021 at 06:54:36AM +1100, Chris Angelico wrote: [...] > Teaching moment. Currently, the equivalent second function would be this: > > def f2(l=None): > if l is None: l = [] > l.append(4) > return l > > And the whole "early bind or late bind" question is there just the > same; the only difference is that the late binding happens somewhere > inside the function body, instead of being visible as part of the > function's header. (In this toy example, it's the very next line, > which isn't a major problem; but in real-world examples, it's often > buried deeper in the function, and it's not obvious that passing None > really is the same as passing the array's length, or using a system > random number generator, or constructing a new list, or whatever it > is.)
I challenge that assertion. I've never knowingly seen a function where the late binding is "buried deeper in the function", certainly not deep enough that it is not obvious. It is a very strong convention that such late binding operations occur early in the function body. You know, before you use the parameter, not afterwards *wink* But then I mostly look at well-written functions that are usually less than two, maybe three, dozen lines long, with a managable number of parameters. If you are regularly reading badly-written functions that are four pages long, with fifty parameters, your experience may differ :-) The bisect function you gave earlier is a real-world example of a non-toy function. You will notice that the body of bisect_right: - does the late binding early in the body, immediately after checking for an error condition; - and is a manageable size (19 LOC). https://github.com/python/cpython/blob/3.10/Lib/bisect.py The bisect module is also good evidence that this proposal may not be as useful as we hope. We have: def insort_right(a, x, lo=0, hi=None, *, key=None): which just passes the None on to bisect_right. So if we introduced optional late-binding, the bisect module has two choices: - keep the status quo (don't use the new functionality); - or violate DRY (Don't Repeat Yourself) by having both functions duplicate the same late-binding. It's only a minor DRY violation, but still, if the bisect module was mine, I wouldn't use the new late-binding proposal. So I think that your case is undermined a little by your own example. -- Steve _______________________________________________ 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/PQESO4G5LXCJBCN5LNYL5PFUAIPIOS65/ Code of Conduct: http://python.org/psf/codeofconduct/
