From: Masklinn <masklinn@masklinn.net> Sent: Friday, February 21, 2014 2:43 PM
Also, I don't find the idea of having a builtin construct for such hacks a good idea. Libs for which this may be practicle can return self --end of
On 2014-02-21, at 23:00 , spir <denis.spir@gmail.com> wrote: the story.
That has two issues though:
1. it makes chainability a decision of the library author, the library user gets to have no preference. This means e.g. you can't create a tree of elements in ElementTree in a single expression (AFAIK Element does not take children parameters). With cascading, the user can "chain" a library whose author did not choose to support chaining (in fact with cascading no author would ever need to support chaining again).
2. where a return value can make sense (and be useful) the author *must* make a choice. No way to chain `dict.pop()` since it returns the popped value, even if `pop` was only used for its removal-with-shut-up properties. With cascading the user can have his cake and eat it: he gets the return value if he wants it, and can keep "chaining" if he does not care.
I think this is almost always a bad thing to do, and a feature that encourages/enables it is a bad feature just for that reason. If you just want to remove an element from a list or a dict, you use a del statement. There's no reason to call pop unless you want to result. Misusing pop to allow you to wedge a statement into an expression is exactly the same as any other misuse, akin to the "os.remove(path) except IOError: None" from the other thread. Look at it this way: If someone wrote this, would you congratulate him on his cleverness, or ask him to fix it before you waste time reviewing his code? [d.pop(key) for key in get_keys()]