On Sun, 14 Nov 2010 22:39:05 -0800, Dmitry Groshev wrote: > Here are some proposals. They are quite useful at my opinion and I'm > interested for suggestions. It's all about some common patterns. First > of all: how many times do you write something like > t = foo() > t = t if pred(t) else default_value > ?
Hardly ever. Not often enough to need special syntax for it. Of course we can write it as > t = foo() if pred(foo()) else default_value > but here we have 2 foo() calls instead of one. Why can't we write just > something like this: > t = foo() if pred(it) else default_value > where "it" means "foo() value"? t = foo()+bar()+baz() if pred(it) else baz()-foo()-bar() What does "it" mean here? > Second, I saw a lot of questions about using dot notation for a > "object-like" dictionaries and a lot of solutions like this: > class dotdict(dict): > def __getattr__(self, attr): > return self.get(attr, None) > __setattr__= dict.__setitem__ > __delattr__= dict.__delitem__ > why there isn't something like this in a standart library? Because dot notation for dictionaries is not something we should encourage. > And the > third. The more I use python the more I see how "natural" it can be. By > "natural" I mean the statements like this: > [x.strip() for x in reversed(foo)] > which looks almost like a natural language. But there is some pitfalls: > if x in range(a, b): #wrong! Why do you say it's wrong? It's perfectly correct: 1 in range(1, 10) => returns True 1.5 in range(1, 10) => returns False 5 in range(1, 10) => returns True 10 in range(1, 10) => returns False exactly as I expect for element testing in a half-open interval. So where's the problem? If you want interval testing, you need to perform an interval test, not an element test. > it feels so natural to check it that way, but we have to write > if a <= x <= b > I understand that it's not a big deal, but it would be awesome to have > some optimisations - it's clearly possible to detect things like that > "wrong" one and fix it in a bytecode. If I write: x in range(1, 10) how do you expect the compiler to read my mind and know if I want the half-open interval or the closed interval? -- Steven -- http://mail.python.org/mailman/listinfo/python-list
