Do these count as “idioms”? Are these problems commonly messed up? I sampled a dozen or so and all the ones I saw are snippets for doing really basic tasks, but didn’t seem particularly idiomatic, nor like tasks that cause a lot of bugs...
I don’t know what you understand an ‘idiom’ is, but being commonly misunderstood or a common source of errors is nothing to do with being an idiom. I don’t know how getting the size of an array could not be idiomatic.
Sorry I wasn't clear. I was responding to two different claims made in the title of this site: first that the samples are "idioms", and second that people should avoid reinventing the wheel in production code. It's not clear to me how these samples accomplish either.
"Idiom" means something that is done in a characteristic style. For example, in Python, it's idiomatic to use list comprehensions rather than for loops.
I don't see how getting the size of an array could be idiomatic in that sense, because there is always only a single way to do it, it's never a stylistic choice.
Python certainly makes some of the tasks so simple as to be moot. But some people try to bend a new language to match what they're used to.
For example, R is a statistical programming language where almost all data structures and operations are for vectors or arrays. But it's not unusual to see people on StackOverflow or blogs reinventing wheels like map/reduce/filter with for loops. I agree it's just inexperience that led to it, but the "intended" way is still idiomatic.
