Note: the syntactic extensions to yield make it use very similar to that in Ruby. This is intentional.

They finally got it. The snakes finally figured out that anonymous blocks are what sets Ruby apart from Python and allows you to do all sorts of cool things in Ruby that can’t be done (as easily) in Python. For years the snake people have been repeating the mantra that there’s nothing you can do in Ruby that can’t be done in Python.

Well, we’ll still have the sky punchers.

But how does this match with Guido’s intention to get rid of lambda’s in an upcoming version of Python? Seems to be a bit of a contradiction. Also, will python’s proposed anonymous blocks allow for more than one statement? Stay tuned. For now I don’t think we’ll lose any Rubyists to the Snake.

And when will Ruby get Python’s list comprehensions? I think this is one of the biggest downsides of Ruby. I dare anyone to write the second line of the code shown in this page in Ruby as elegantly as the Python version.

lesbonics,

As a non-Python programmer, I find the above to be almost unreadable, and much prefer the Ruby map style.

If you’re still interested in list comprehensions for Ruby, someone wrote a short implementation of them once. See somewhere on ruby-talk.

Sorry, Array.new(3) {|i| buttons.collect {|button| button[i].chr}} is the best I can do, but my powers are weak.

P.S If you want to match line length to the Python version, [i].chr can be replaced with the not as understandable [i, 1]. If you want.

P.P.S If you want even less line length, collect’s alias, map, could be used.

Sorry, I got ahead of myself with the P.S above. Matching line length requires map.

indexes = [[letters[i] for letters in buttons] for i in range(3)]
indexes = (0..2).map{|i| buttons.map{|button| b[i].chr}}

The solution in Ruby can be read left-to-right, Python’s requires one to parse the whole expr. to find the indices used in the iteration. It is arguably easier to remember the indices than the expression being evaluated.

There are some things one can express more easily with list comprehensions. The above is not one of them. Better luck next time, lesbo.

I’d have found more interesting an example of a list comprehension using mapping and filtering. Not really harder to do in ruby (see map_filter on the wiki) but at least not builtin :)

Another option:

buttons.map{|button| button[0..2].scan(/./)}.transpose

I love Ruby.

Here are some more Python variants for that code.

>>> buttons = ["abc", "def", "ghi"]
>>> zip(*buttons)[:3]
[('a', 'd', 'g'), ('b', 'e', 'h'), ('c', 'f', 'i')]
>>> zip(*[s[:3] for s in buttons])
[('a', 'd', 'g'), ('b', 'e', 'h'), ('c', 'f', 'i')]
>>> 
>>> from itertools import islice, izip 
>>> list(islice(izip(*buttons), 3))
[('a', 'd', 'g'), ('b', 'e', 'h'), ('c', 'f', 'i')]
>>> 

The first works best for the original purpose. The latter two are increasingly more memory efficient. This isn’t a case where list comps shine.

Sorry about the > (or should I write >? or >?) The preview button appears to use different escaping rules than the submit.