[fuzzyman]

As a Pythonista I have no idea what the Ruby snippet is doing. Readability depends entirely on context.

The Python 3 version is using a function annotation.

In Python 2 or 3 you could use a context manager (with statement) to similar effect.

[aerique]

As a Pythonista I have no idea what the Ruby snippet is doing. Readability depends entirely on context.

Oh, come on. You're just disagreeing for effect here.

I've never used Ruby but that snippet is clear as day.

The Python 3 snippet suggests to me that the output would be "/hi" though :)

[Confusion]

  Oh, come on. You're just disagreeing for effect here.
  I've never used Ruby but that snippet is clear as day.

The hell it is. I find it quite confusing. I'll take the Python 2 solution anyday, which clearly seperates what is called from when it is called. One of the main problems with the 'my language is so flexible' approach is that inventing concise solutions becomes a goal in itself.

[steveklabnik]

> which clearly seperates what is called from when it is called

You're passing some code as an argument to a function. Many other languages do this. Do you hate Lisp and Haskell, too? Do you not use continuations in Python? Or callback functions?

[Confusion]

If you pass a function as an argument to a function, you're still separating what from when: the function declaration shows what; the invocation of the function shows when. It doesn't matter whether it's

  def foo(f):
    f()

or

  (define (foo f) (f))

That has nothing to do with annotating a function to show it binds to some URL and is invoked when an HTTP GET request is received with that URL. I don't like having to scroll through a source file to discover such bindings and I actually prefer them to be defined at a separate place. In that sense, the Python 2 solution isn't good either and suffers from the same problem I described earlier: people try to be so concise that they loose sight of other goals.

[steveklabnik]

The Ruby code is not an annotation. It's very close to passing an anonymous function to a function. The definition of get is

    def get(path, opts={}, &block)

See that &block? Here's the actual source of get:

      # Defining a `GET` handler also automatically defines
      # a `HEAD` handler.
      def get(path, opts={}, &block)
        conditions = @conditions.dup
        route('GET', path, opts, &block)
 
        @conditions = conditions
        route('HEAD', path, opts, &block)
      end

Think of it as "I'm registering this block as a callback, to be called when this url is processed." I'm not sure how else you'd like to have a web DSL written; every web library I've used has worked this way.

[Confusion]

The Ruby code is not an annotation.

Which is exactly the problem: it should be, because it is meta-information about when the function is supposed to be called. It's not a good idea to wrap that into a function, together with the code that is supposed to be executed, because you are mixing two completely different kinds of information into some new function. This code is being too clever for it's own good: it condenses information so far that you are forced to think harder about what each piece means. I consider this is one of the main dangers of languages like Ruby: it's proponents lose sight of the fact that they are coming full circle, back to writing code that's so clever that no one in the future will understand it.

every web library I've used has worked this way.

I doubt that we've used a disjoint set of web libraries, so my only answer can be: no, they haven't worked that way. Most libraries map paths to named functions separately from implementing the functions.

Conciseness is not an ultimate goal; in fact, it is rather the opposite, as those that suffered under the clever C hacks of others will tell you. To paraphrase Santanyana: people have forgotten the past and are repeating it.

[rbanffy]

> Oh, come on. You're just disagreeing for effect here.

It's unclear what "get" is. Is it a function? What does it return? My guess would be that it returns a function bound to the handler of a "/hi" url, but that's a guess.

[steveklabnik]

"get" is a function that takes a string and a block.

And the block is bound to the uri given in the string, so your guess is correct.

[rbanffy]

Ruby always confuses me with this flexible syntax...

[steveklabnik]

It's possible that you just haven't read enough ruby, then. There are only two variations on the syntax of passing a block to a function, "do/end" and "{ }". By convention, multiline blocks use do/end, and single line blocks use {}.

It's also possible that one of the things in the article is the gotcha, flexible parenthesis. By convention, Rubyists tend to use parenthesis when defining functions, but not when calling them:

    def get(path, opts={}, &block)

    get "/hello" do

not

    get("hello") do

Which would still work, if you preferred. The exception to this is chaining method calls:

    Users.find_all_by_age(23).select {|user| user.first_name == "steve" }

... not that that's an awesome use of ActiveRecord, but whatever.

[steveklabnik]

> As a Pythonista I have no idea what the Ruby snippet is doing.

Fair enough. Arguing over beauty is silly anyway, I just wanted to point out that the entire thing is entirely subjective.

> The Python 3 version is using a function annotation.

Thanks, checking out PEP 3107 now. I've always seen annotations done with the @annotation syntax like the Python 2 snippet has.

[algorias]

> Thanks, checking out PEP 3107 now. I've always seen annotations done with the @annotation syntax like the Python 2 snippet has.

The @ syntax is for decorators. Different beast altogether.

[steveklabnik]

Ah. So, Python uses the Java annotation syntax for decorators? Hm. One more thing I'll have to look into when I get the time.

[rbanffy]

Actually, I think Java uses Python decoration syntax for annotations, but I have been wrong before.

[pmiller2]

I'm pretty sure Python picked it up after Java did. But, I don't think it's a case of imitation; it's just that the glyph '@' happened not to have syntactic meaning attached to it and it looks okay.

[blasdel]

No, they're exactly the same beast!

I've used decorators to add attributes to function objects in several projects in the past -- you don't have to wrap the original.