c#(好吧，我猜一部分是VisualStudio IDE):

No covariance (yet), like Class<D> cannot be used in place of Class<B> even though type D derives from type B. Graphic designers don't support generic based inheritance (or inheritance from abstract classes), even though the inheritance itself works just fine if you work around the designer problems by adding extra inheritance levels just so designers always see concrete non-generic variants of your code. No constructor inheritance No constructors in where clauses of generic type parameters VisualStudio seems to have a tendency to mysteriously check out files (like project files and/or unit test definitions) when opening a solution, even though the files do not seem to actually get altered.

如果你明天再问我，可能会有不同的名单。即使协方差和设计师的麻烦将在我的前5名，直到他们被解决(随着方差添加到c# 4.0，这似乎已经发生了至少一个…)

不得不假设我们有语言。我们做什么?

Python (3.1)

奇怪的无序T if C else F语法用于条件语句。 字节字面值看起来太像STR字面值了。我们应该得到x'414243'而不是b' abc '。 str在某些平台上是UTF-16，在其他平台上是UTF-32。(尽管至少比2要好。x字符串。) 具有相同的加法和连接运算符。这对numpy.array这样的类型很不利。 运行缓慢。

Python:

没有分隔符表示块的结束会导致歧义，这样自动缩进就不能处理格式不佳的代码。 没有宏(修饰符不算) 没有像haskell的cabal或perl的CPAN那样的库自动获取 不能声明变量const(是的，可以自己定义变量，但是…) 元编程被削弱 差点忘了全局解释器锁

Scala是我最喜欢的语言。五件讨厌的事?容易:

Takes a long time to learn properly. I know you can write Scala as a 'better java'. That is what we used to say about C++ and C too. I agree this is an inevitable consequence of the deep ideas in the language. But still ... Methods vs. Functions: def f(x: Int) = x*x defines a method f, not a function f. Methods are not functions despite a lot of early Scala tutorial material blurring the distinction. The language tries to blur it too because if you supply a method in some places where a function is expected it is accepted. Do we have to have both methods and functions? Yes it is fundamental. But it was initially confusing to me. Composing classes or objects from mixins in the 'cake' pattern is prone to NPE's. e.g. trait X { val host: String; val url = "http://" + host } is a mixin that will NPE on instantiation, or not, depending on its position in the class declaration. The compiler could tell you if it will fail but doesn't. (In 2.7 anyway.) It is hard to diagnose the problem in complex inheritance graphs. Arrays in 2.8 rely on implicits to mesh with the main scala collection types. But implicits are not applied everywhere. An Array can be supplied where a Seq is expected. But an Option[Array] cannot be supplied where an Option[Seq] is expected. I know there are no completely 'right' ways to handle java Arrays. Type erasure. Enough said.

Python,:

No switch keyword. And NO, dictionary is not a replacement for it. Not even a bunch of elif statements. Inconsistent line break handling. Why can I do: test = (1, 2, 3) And not: from itertools import cycle, islice, izip Why can't I do: if stuff \ and foo \ or bar: return "Formated string with %(arg)s" % \ {'arg': "bloody slash"} without using slashes? There is not one obvious and only one way to do it. Python fails on its motto just like Java failed on "Write once run anywhere". # what somebody from an another language would do if not test.has_key('foo'): test['foo'] = 0 n = test['foo'] = test['foo'] + 1 vs # what an agnostic beginer would do try: test['foo'] += 1 except KeyError: test['foo'] = 1 n = test['foo'] vs # what you end up after looking for dictionary default value in the python doc test.setdefault('foo', 0) n = test['foo'] = test['foo'] + 1 vs # what I would do n = test['foo'] = test.get('foo', 0) + 1 And the worst is that they don't do exactly the same thing. There are subtle differences. Choice between spaces and tabs. There should be no choice. Pick on, set it in stone and stop fighting. Why can you do that: test = {} test['foo'] = 0 but not: test = [] test[] = 0

附注:" ".join(l)是优秀的人。不要抱怨它，这并不明显，但考虑到迭代器模式，这是正确的方法。