On Fri, 30 Sep 2016 03:06 pm, Rustom Mody wrote: > On Friday, September 30, 2016 at 10:23:31 AM UTC+5:30, Gregory Ewing > wrote: >> namenobodywants wrote: >> > can anyone help to reconcile me to this semantics? >> >> Not really. Most people agree that it's not desirable >> behaviour, but we've ended up here due to a convoluted >> history, and there doesn't seem to be a good way to >> fix it without breaking a lot of existing code. > > Thanks for an unusually helpful answer. > > In my experience telling a beginner: > «This» is a misfeature/gotcha > And «this» is its workaround > > greatly shortens the learning curve as compared to long-winded > justificatory explanations
What happens if it is *not* a misfeature? Gotchas are not always misfeatures -- sometimes gotchas are gotchas because people's expectations are simply wrong, and pandering to their confused expectations does not actually help them. I haven't made up my mind about *this* specific (mis)feature itself. I know I don't want for-loops to introduce their own scope, but that doesn't mean that the binding behaviour inside for-loops is necessarily the best way of doing it. I'm still thinking about it. But *in general*, people often don't think the logical consequences through before deciding what behaviour is "obviously" right. They insist that whatever behaviour would be convenient for them *now* is the one and only correct way of doing things -- even if, an hour later, the *opposite* behaviour is convenient and therefore the correct way of doing things. Obviously late binding is the one and only correct way of setting function parameter defaults -- until we need early binding, then it is the one and only correct way of doing it. Gotchas usually exist for a reason. Very few programming languages design gotchas into them to deliberately trip people up[1], or even through carelessness. More often, they're the unexpected consequences of a series of sensible, or even unavoidable, decisions. [1] "When I design my killer language, the identifiers `foo` and `bar` will be reserved words, never used, and not even mentioned in the reference manual. Any program using one will simply dump core without comment. Multitudes will rejoice." - Tim Peters -- Steve “Cheer up,” they said, “things could be worse.” So I cheered up, and sure enough, things got worse. -- https://mail.python.org/mailman/listinfo/python-list
