What does Ruby have that Python doesn't, and vice versa?

Question

There is a lot of discussions of Python vs Ruby, and I all find them completely unhelpful, because they all turn around why feature X sucks in language Y, or that claim language Y doesn't have X, although in fact it does. I also know exactly why I prefer Python, but that's also subjective, and wouldn't help anybody choosing, as they might not have the same tastes in development as I do.

It would therefore be interesting to list the differences, objectively. So no "Python's lambdas sucks". Instead explain what Ruby's lambdas can do that Python's can't. No subjectivity. Example code is good!

Don't have several differences in one answer, please. And vote up the ones you know are correct, and down those you know are incorrect (or are subjective). Also, differences in syntax is not interesting. We know Python does with indentation what Ruby does with brackets and ends, and that @ is called self in Python.

UPDATE: This is now a community wiki, so we can add the big differences here.

Ruby has a class reference in the class body

In Ruby you have a reference to the class (self) already in the class body. In Python you don't have a reference to the class until after the class construction is finished.

An example:

class Kaka
  puts self
end

self in this case is the class, and this code would print out "Kaka". There is no way to print out the class name or in other ways access the class from the class definition body in Python (outside method definitions).

All classes are mutable in Ruby

This lets you develop extensions to core classes. Here's an example of a rails extension:

class String
  def starts_with?(other)
    head = self[0, other.length]
    head == other
  end
end

Python (imagine there were no ''.startswith method):

def starts_with(s, prefix):
    return s[:len(prefix)] == prefix

You could use it on any sequence (not just strings). In order to use it you should import it explicitly e.g., from some_module import starts_with.

Ruby has Perl-like scripting features

Ruby has first class regexps, $-variables, the awk/perl line by line input loop and other features that make it more suited to writing small shell scripts that munge text files or act as glue code for other programs.

Ruby has first class continuations

Thanks to the callcc statement. In Python you can create continuations by various techniques, but there is no support built in to the language.

Ruby has blocks

With the "do" statement you can create a multi-line anonymous function in Ruby, which will be passed in as an argument into the method in front of do, and called from there. In Python you would instead do this either by passing a method or with generators.

Ruby:

amethod { |here|
    many=lines+of+code
    goes(here)
}

Python (Ruby blocks correspond to different constructs in Python):

with amethod() as here: # `amethod() is a context manager
    many=lines+of+code
    goes(here)

Or

for here in amethod(): # `amethod()` is an iterable
    many=lines+of+code
    goes(here)

Or

def function(here):
    many=lines+of+code
    goes(here)

amethod(function)     # `function` is a callback

Interestingly, the convenience statement in Ruby for calling a block is called "yield", which in Python will create a generator.

Ruby:

def themethod
    yield 5
end

themethod do |foo|
    puts foo
end

Python:

def themethod():
    yield 5

for foo in themethod():
    print foo

Although the principles are different, the result is strikingly similar.

Ruby supports functional style (pipe-like) programming more easily

myList.map(&:description).reject(&:empty?).join("\n")

Python:

descriptions = (f.description() for f in mylist)
"\n".join(filter(len, descriptions))

Python has built-in generators (which are used like Ruby blocks, as noted above)

Python has support for generators in the language. In Ruby 1.8 you can use the generator module which uses continuations to create a generator from a block. Or, you could just use a block/proc/lambda! Moreover, in Ruby 1.9 Fibers are, and can be used as, generators, and the Enumerator class is a built-in generator 4

docs.python.org has this generator example:

def reverse(data):
    for index in range(len(data)-1, -1, -1):
        yield data[index]

Contrast this with the above block examples.

Python has flexible name space handling

In Ruby, when you import a file with require, all the things defined in that file will end up in your global namespace. This causes namespace pollution. The solution to that is Rubys modules. But if you create a namespace with a module, then you have to use that namespace to access the contained classes.

In Python, the file is a module, and you can import its contained names with from themodule import *, thereby polluting the namespace if you want. But you can also import just selected names with from themodule import aname, another or you can simply import themodule and then access the names with themodule.aname. If you want more levels in your namespace you can have packages, which are directories with modules and an __init__.py file.

Python has docstrings

Docstrings are strings that are attached to modules, functions and methods and can be introspected at runtime. This helps for creating such things as the help command and automatic documentation.

def frobnicate(bar):
    """frobnicate takes a bar and frobnicates it

       >>> bar = Bar()
       >>> bar.is_frobnicated()
       False
       >>> frobnicate(bar)
       >>> bar.is_frobnicated()
       True
    """

Ruby's equivalent are similar to javadocs, and located above the method instead of within it. They can be retrieved at runtime from the files by using 1.9's Method#source_location example use

Python has more libraries

Python has a vast amount of available modules and bindings for libraries.

Python has multiple inheritance

Ruby does not ("on purpose" -- see Ruby's website, see here how it's done in Ruby). It does reuse the module concept as a type of abstract classes.

Python has list/dict comprehensions

Python:

res = [x*x for x in range(1, 10)]

Ruby:

res = (0..9).map { |x| x * x }

Python:

>>> (x*x for x in range(10))
<generator object <genexpr> at 0xb7c1ccd4>
>>> list(_)
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

Ruby:

p = proc { |x| x * x }
(0..9).map(&p)

Python 2.7+:

>>> {x:str(y*y) for x,y in {1:2, 3:4}.items()}
{1: '4', 3: '16'}

Ruby:

>> Hash[{1=>2, 3=>4}.map{|x,y| [x,(y*y).to_s]}]
=> {1=>"4", 3=>"16"}

Python has decorators

Things similar to decorators can also be created in Ruby, and it can also be argued that they aren't as necessary as in Python.

Syntax differences

Ruby requires "end" or "}" to close all of its scopes, while Python uses white-space only. There have been recent attempts in Ruby to allow for whitespace only indentation http://github.com/michaeledgar/seamless

Answer 1

You can have code in the class definition in both Ruby and Python. However, in Ruby you have a reference to the class (self). In Python you don't have a reference to the class, as the class isn't defined yet.

An example:

def Kaka
  puts self
end

self in this case is the class, and this code would print out "Kaka". There is no way to print out the class name or in other ways access the class from the class definition body in Python.

Answer 2

Ruby has the concepts of blocks, which are essentially syntactic sugar around a section of code; they are a way to create closures and pass them to another method which may or may not use the block. A block can be invoked later on through a yield statement.

For example, a simple definition of an each method on Array might be something like:

class Array
  def each
    for i in self  
      yield(i)     # If a block has been passed, control will be passed here.
    end  
  end  
end

Then you can invoke this like so:

# Add five to each element.
[1, 2, 3, 4].each{ |e| puts e + 5 }
> [6, 7, 8, 9]

Python has anonymous functions/closures/lambdas, but it doesn't quite have blocks since it's missing some of the useful syntactic sugar. However, there's at least one way to get it in an ad-hoc fashion. See, for example, here.

Answer 3

Python has docstrings and ruby doesn't... Or if it doesn't, they are not accessible as easily as in python.

Ps. If im wrong, pretty please, leave an example? I have a workaround that i could monkeypatch into classes quite easily but i'd like to have docstring kinda of a feature in "native way".

Answer 4

What Ruby has over Python are its scripting language capabilities. Scripting language in this context meaning to be used for "glue code" in shell scripts and general text manipulation.

These are mostly shared with Perl. First-class built-in regular expressions, $-Variables, useful command line options like Perl (-a, -e) etc.

Together with its terse yet epxressive syntax it is perfect for these kind of tasks.

Python to me is more of a dynamically typed business language that is very easy to learn and has a neat syntax. Not as "cool" as Ruby but neat. What Python has over Ruby to me is the vast number of bindings for other libs. Bindings to Qt and other GUI libs, many game support libraries and and and. Ruby has much less. While much used bindings e.g. to Databases are of good quality I found niche libs to be better supported in Python even if for the same library there is also a Ruby binding.

So, I'd say both languages have its use and it is the task that defines which one to use. Both are easy enough to learn. I use them side-by-side. Ruby for scripting and Python for stand-alone apps.

Answer 5

Ruby has ugly syntax, Python does not. :P

Answer 6

While the functionalty is to a great extent the same (especially in the Turing sense), malicious tongues claim that Ruby was created for Pythonistas that could not split up with the Perlish coding style.

Answer 7

I don't think "Ruby has X and Python doesn't, while Python has Y and Ruby doesn't" is the most useful way to look at it. They're quite similar languages, with many shared abilities.

To a large degree, the difference is what the language makes elegant and readable. To use an example you brought up, both do theoretically have lambdas, but Python programmers tend to avoid them, and constructs made using them do not look anywhere near as readable or idiomatic as in Ruby. So in Python, a good programmer will want to take a different route to solving the problem than he would in Ruby, just because it actually is the better way to do it.

Answer 8

Python has a "we're all adults here" mentality. Thus, you'll find that Ruby has things like constants while Python doesn't (although Ruby's constants only raise a warning). The Python way of thinking is that if you want to make something constant, you should put the variable names in all caps and not change it.

For example, Ruby:

>> PI = 3.14
=> 3.14
>> PI += 1
(irb):2: warning: already initialized constant PI
=> 4.14

Python:

>>> PI = 3.14
>>> PI += 1
>>> PI
4.1400000000000006

Answer 9

Ruby has sigils and twigils, Python doesn't.

Edit: And one very important thing that I forgot (after all, the previous was just to flame a little bit :-p):

Python has a JIT compiler (Psyco), a sightly lower level language for writing faster code (Pyrex) and the ability to add inline C++ code (Weave).

Answer 10

Ruby has builtin continuation support using callcc.

Hence you can implement cool things like the amb-operator

Answer 11

Python has an explicit, builtin syntax for list-comprehenions and generators whereas in Ruby you would use map and code blocks.

Compare

list = [ x*x for x in range(1, 10) ]

to

res = (1..10).map{ |x| x*x }

Answer 12

I'm unsure of this, so I add it as an answer first.

Python treats unbound methods as functions

That means you can call a method either like theobject.themethod() or by TheClass.themethod(anobject).

Edit: Although the difference between methods and functions is small in Python, and non-existant in Python 3, it also doesn't exist in Ruby, simply because Ruby doesn't have functions. When you define functions, you are actually defining methods on Object.

But you still can't take the method of one class and call it as a function, you would have to rebind it to the object you want to call on, which is much more obstuse.

Answer 13

Some others from:

http://www.ruby-lang.org/en/documentation/ruby-from-other-languages/to-ruby-from-python/

(If I have misintrepreted anything or any of these have changed on the Ruby side since that page was updated, someone feel free to edit...)

Strings are mutable in Ruby, not in Python (where new strings are created by "changes").

Ruby has some enforced case conventions, Python does not.

Python has both lists and tuples (immutable lists). Ruby has arrays corresponding to Python lists, but no immutable variant of them.

In Python, you can directly access object attributes. In Ruby, it's always via methods.

In Ruby, parentheses for method calls are usually optional, but not in Python.

Ruby has public, private, and protected to enforce access, instead of Python’s convention of using underscores and name mangling.

Python has multiple inheritance. Ruby has "mixins."

And another very relevant link:

http://c2.com/cgi/wiki?PythonVsRuby

Which, in particular, links to another good one by Alex Martelli, who's been also posting a lot of great stuff here on SO:

http://groups.google.com/group/comp.lang.python/msg/028422d707512283

Answer 14

You can import only specific functions from a module in Python. In Ruby, you import the whole list of methods. You could "unimport" them in Ruby, but it's not what it's all about.

EDIT:

let's take this Ruby module :

module Whatever
  def method1
  end

  def method2
  end
end

if you include it in your code :

include Whatever

you'll see that both method1 and method2 have been added to your namespace. You can't import only method1. You either import them both or you don't import them at all. In Python you can import only the methods of your choosing. If this would have a name maybe it would be called selective importing?

Answer 15

Ruby has a line by line loop over input files (the '-n' flag) from the commandline so it can be used like AWK. This Ruby one-liner:

ruby -ne 'END {puts $.}'

will count lines like the AWK one-liner:

awk 'END{print NR}'

Ruby gets feature this through Perl, which took it from AWK as a way of getting sysadmins on board with Perl without having to change the way they do things.

Answer 16

Python Example

Functions are first-class variables in Python. You can declare a function, pass it around as an object, and overwrite it:

def func(): print "hello"
def another_func(f): f()
another_func(func)

def func2(): print "goodbye"
func = func2

This is a fundamental feature of modern scripting languages. JavaScript and Lua do this, too. Ruby doesn't treat functions this way; naming a function calls it.

Of course, there are ways to do these things in Ruby, but they're not first-class operations. For example, you can wrap a function with Proc.new to treat it as a variable--but then it's no longer a function; it's an object with a "call" method.

Ruby's functions aren't first-class objects

Ruby functions aren't first-class objects. Functions must be wrapped in an object to pass them around; the resulting object can't be treated like a function. Functions can't be assigned in a first-class manner; instead, a function in its container object must be called to modify them.

def func; p "Hello" end
def another_func(f); method(f)[] end
another_func(:func)      # => "Hello"

def func2; print "Goodbye!"
self.class.send(:define_method, :func, method(:func2))
func                     # => "Goodbye!"

method(:func).owner      # => Object
func                     # => "Goodbye!"
self.func                # => "Goodbye!"    

Answer 17

python has named optional arguments

def func(a, b=2, c=3):
    print a, b, c

>>> func(1)
1 2 3
>>> func(1, c=4)
1 2 4

AFAIK Ruby has only positioned arguments because b=2 in the function declaration is an affectation that always append.

Answer 18

"Variables that start with a capital letter becomes constants and can't be modified"

Wrong. They can.

You only get a warning if you do.

Answer 19

I would like to mention Python descriptor API that allows one customize object-to-attribute "communication". It is also noteworthy that, in Python, one is free to implement an alternative protocol via overriding the default given through the default implementation of the __getattribute__ method. Let me give more details about the aforementioned. Descriptors are regular classes with __get__, __set__ and/or __delete__ methods. When interpreter encounters something like anObj.anAttr, the following is performed:

• __getattribute__ method of anObj is invoked
• __getattribute__ retrieves anAttr object from the class dict
• it checks whether abAttr object has __get__, __set__ or __delete__ callable objects
• the context (i.e., caller object or class, and value, instead of the latter, if we have setter) is passed to the callable object
• the result is returned.

As was mentioned, this is the default behavior. One is free to change the protocol by re-implementing __getattribute__.

This technique is lot more powerful than decorators.

Answer 20

Surprised to see nothing mentioned of ruby's "method missing" mechanism. I'd give examples of the find_by_... methods in Rails, as an example of the power of that language feature. My guess is that something similar could be implemented in Python, but to my knowledge it isn't there natively.

Answer 21

Ruby has embedded documentation:

 =begin

 You could use rdoc to generate man pages from this documentation

 =end

Answer 22

My python's rusty, so some of these may be in python and i just don't remember/never learned in the first place, but here are the first few that I thought of:

Whitespace

Ruby handles whitespace completely different. For starters, you don't need to indent anything (which means it doesn't matter if you use 4 spaces or 1 tab). It also does smart line continuation, so the following is valid:

def foo(bar,
        cow)

Basically, if you end with an operator, it figures out what is going on.

Mixins

Ruby has mixins which can extend instances instead of full classes:

module Humor
  def tickle
    "hee, hee!"
  end
end
a = "Grouchy"
a.extend Humor
a.tickle    »  "hee, hee!"

Enums

I'm not sure if this is the same as generators, but as of Ruby 1.9 ruby as enums, so

>> enum = (1..4).to_enum
=> #<Enumerator:0x1344a8>

Reference: http://blog.nuclearsquid.com/writings/ruby-1-9-what-s-new-what-s-changed

"Keyword Arguments"

Both of the items listed there are supported in Ruby, although you can't skip default values like that. You can either go in order

def foo(a, b=2, c=3)
  puts "#{a}, #{b}, #{c}"
end
foo(1,3)   >> 1, 3, 3
foo(1,c=5) >> 1, 5, 3
c          >> 5

Note that c=5 actually assigns the variable c in the calling scope the value 5, and sets the parameter b the value 5.

or you can do it with hashes, which address the second issue

def foo(a, others)
  others[:b] = 2 unless others.include?(:b)
  others[:c] = 3 unless others.include?(:c)
  puts "#{a}, #{others[:b]}, #{others[:c]}"
end
foo(1,:b=>3) >> 1, 3, 3
foo(1,:c=>5) >> 1, 2, 5

Reference: The Pragmatic Progammer's Guide to Ruby

Answer 23

I'd like to suggest a variant of the original question, "What does Ruby have that Python doesn't, and vice versa?" which admits the disappointing answer, "Well, what can you do with either Ruby or Python that can't be done in Intercal?" Nothing on that level, because Python and Ruby are both part of the vast royal family sitting on the throne of being Turing approximant.

But what about this:

What can be done gracefully and well in Python that can't be done in Ruby with such beauty and good engineering, or vice versa?

That may be much more interesting than mere feature comparison.

Answer 24

From Ruby's website:

Similarities As with Python, in Ruby,...

• There’s an interactive prompt (called irb).
• You can read docs on the command line (with the ri command instead of pydoc).
• There are no special line terminators (except the usual newline).
• String literals can span multiple lines like Python’s triple-quoted strings.
• Brackets are for lists, and braces are for dicts (which, in Ruby, are called “hashes”).
• Arrays work the same (adding them makes one long array, but composing them like this a3 = [ a1, a2 ] gives you an array of arrays).
• Objects are strongly and dynamically typed.
• Everything is an object, and variables are just references to objects.
• Although the keywords are a bit different, exceptions work about the same.
• You’ve got embedded doc tools (Ruby’s is called rdoc).

Differences Unlike Python, in Ruby,...

• Strings are mutable.
• You can make constants (variables whose value you don’t intend to change).
• There are some enforced case-conventions (ex. class names start with a capital letter, variables start with a lowercase letter).
• There’s only one kind of list container (an Array), and it’s mutable.
• Double-quoted strings allow escape sequences (like \t) and a special “expression substitution” syntax (which allows you to insert the results of Ruby expressions directly into other strings without having to "add " + "strings " + "together"). Single-quoted strings are like Python’s r"raw strings".
• There are no “new style” and “old style” classes. Just one kind.
• You never directly access attributes. With Ruby, it’s all method calls.
• Parentheses for method calls are usually optional.
• There’s public, private, and protected to enforce access, instead of Python’s _voluntary_ underscore __convention__.
• “mixin’s” are used instead of multiple inheritance.
• You can add or modify the methods of built-in classes. Both languages let you open up and modify classes at any point, but Python prevents modification of built-ins — Ruby does not.
• You’ve got true and false instead of True and False (and nil instead of None).
• When tested for truth, only false and nil evaluate to a false value. Everything else is true (including 0, 0.0, "", and []).
• It’s elsif instead of elif.
• It’s require instead of import. Otherwise though, usage is the same.
• The usual-style comments on the line(s) above things (instead of docstrings below them) are used for generating docs.
• There are a number of shortcuts that, although give you more to remember, you quickly learn. They tend to make Ruby fun and very productive.

Answer 25

Somewhat more on the infrastructure side:

• Python has much better integration with C++ (via things like Boost.Python, SIP, and Py++) than Ruby, where the options seem to be either write directly against the Ruby interpreter API (which you can do with Python as well, of course, but in both cases doing so is low level, tedious, and error prone) or use SWIG (which, while it works and definitely is great if you want to support many languages, isn't nearly as nice as Boost.Python or SIP if you are specifically looking to bind C++).

• Python has a number of web application environments (Django, Pylons/Turbogears, web.py, probably at least half a dozen others), whereas Ruby (effectively) has one: Rails. (Other Ruby web frameworks do exist, but seemingly have a hard time getting much traction against Rails). Is this aspect good or bad? Hard to say, and probably quite subjective; I can easily imagine arguments that the Python situation is better and that the Ruby situation is better.

• Culturally, the Python and Ruby communities seem somewhat different, but I can only hint at this as I don't have that much experience interacting with the Ruby community. I'm adding this mostly in the hopes that someone who has a lot of experience with both can amplify (or reject) this statement.

Answer 26

Another difference in lambdas between Python and Ruby is demonstrated by Paul Graham's Accumulator Generator problem. Reprinted here:

Write a function foo that takes a number n and returns a function that takes a number i, and returns n incremented by i. Note: (a) that's number, not integer, (b) that's incremented by, not plus.

In Ruby, you can do this:

def foo(n)
  lambda {|i| n += i }
end

In Python, you'd create an object to hold the state of n:

class foo(object):
    def __init__(self, n):
        self.n = n
    def __call__(self, i):
        self.n += i
        return self.n

Some folks might prefer the explicit Python approach as being clearer conceptually, even if it's a bit more verbose. You store state like you do for anything else. You just need to wrap your head around the idea of callable objects. But regardless of which approach one prefers aesthetically, it does show one respect in which Ruby lambdas are more powerful constructs than Python's.

Answer 27

http://c2.com/cgi/wiki?PythonVsRuby
http://c2.com/cgi/wiki?SwitchedFromPythonToRuby
http://c2.com/cgi/wiki?SwitchedFromRubyToPython
http://c2.com/cgi/wiki?UsingPythonDontNeedRuby
http://c2.com/cgi/wiki?UsingRubyDontNeedPython

Answer 28

_{Shamelessly copy/pasted from: Alex Martelli answer on "What's better about Ruby than Python" thread from comp.lang.python mailing list.}

Aug 18 2003, 10:50 am

Erik Max Francis wrote:
> "Brandon J. Van Every" wrote:

>> What's better about Ruby than Python?  I'm sure there's something.
>> What is it?

> Wouldn't it make much more sense to ask Ruby people this, rather than
> Python people?

Might, or might not, depending on one's purposes -- for example, if
one's purposes include a "sociological study" of the Python community,
then putting questions to that community is likely to prove more
revealing of information about it, than putting them elsewhere:-).

Personally, I gladly took the opportunity to follow Dave Thomas'
one-day Ruby tutorial at last OSCON.  Below a thin veneer of syntax
differences, I find Ruby and Python amazingly similar -- if I was
computing the minimum spanning tree among just about any set of
languages, I'm pretty sure Python and Ruby would be the first two
leaves to coalesce into an intermediate node:-).

Sure, I do get weary, in Ruby, of typing the silly "end" at the end
of each block (rather than just unindenting) -- but then I do get
to avoid typing the equally-silly ':' which Python requires at the
_start_ of each block, so that's almost a wash:-).  Other syntax
differences such as '@foo' versus 'self.foo', or the higher significance
of case in Ruby vs Python, are really just about as irrelevant to me.

Others no doubt base their choice of programming languages on just
such issues, and they generate the hottest debates -- but to me that's
just an example of one of Parkinson's Laws in action (the amount on
debate on an issue is inversely proportional to the issue's actual
importance).

**Edit** (by AM 6/19 11:45): this is also known as "painting the
bikeshed" (or, for short, "bikeshedding") -- the reference is, again,
to Northcote Parkinson, who gave "debates on what color to paint the
bikeshed" as a typical example of "hot debates on trivial topics".
(end-of-Edit).

One syntax difference that I do find important, and in Python's
favor -- but other people will no doubt think just the reverse --
is "how do you call a function which takes no parameters".  In
Python (like in C), to call a function you always apply the
"call operator" -- trailing parentheses just after the object
you're calling (inside those trailing parentheses go the args
you're passing in the call -- if you're passing no args, then
the parentheses are empty).  This leaves the mere mention of
_any_ object, with no operator involved, as meaning just a
reference to the object -- in any context, without special
cases, exceptions, ad-hoc rules, and the like.  In Ruby (like
in Pascal), to call a function WITH arguments you pass the
args (normally in parentheses, though that is not invariably
the case) -- BUT if the function takes no args then simply
mentioning the function implicitly calls it.  This may meet
the expectations of many people (at least, no doubt, those
whose only previous experience of programming was with Pascal,
or other languages with similar "implicit calling", such as
Visual Basic) -- but to me, it means the mere mention of an
object may EITHER mean a reference to the object, OR a call
to the object, depending on the object's type -- and in those
cases where I can't get a reference to the object by merely
mentioning it I will need to use explicit "give me a reference
to this, DON'T call it!" operators that aren't needed otherwise.
I feel this impacts the "first-classness" of functions (or
methods, or other callable objects) and the possibility of
interchanging objects smoothly.  Therefore, to me, this specific
syntax difference is a serious black mark against Ruby -- but
I do understand why others would thing otherwise, even though
I could hardly disagree more vehemently with them:-).

Below the syntax, we get into some important differences in
elementary semantics -- for example, strings in Ruby are
mutable objects (like in C++), while in Python they are not
mutable (like in Java, or I believe C#).  Again, people who
judge primarily by what they're already familiar with may
think this is a plus for Ruby (unless they're familiar with
Java or C#, of course:-).  Me, I think immutable strings are
an excellent idea (and I'm not surprised that Java, independently
I think, reinvented that idea which was already in Python), though
I wouldn't mind having a "mutable string buffer" type as well
(and ideally one with better ease-of-use than Java's own
"string buffers"); and I don't give this judgment because of
familiarity -- before studying Java, apart from functional
programming languages where _all_ data are immutable, all the
languages I knew had mutable strings -- yet when I first saw
the immutable-string idea in Java (which I learned well before
I learned Python), it immediately struck me as excellent, a
very good fit for the reference-semantics of a higher level
programming language (as opposed to the value-semantics that
fit best with languages closer to the machine and farther from
applications, such as C) with strings as a first-class, built-in
(and pretty crucial) data type.

Ruby does have some advantages in elementary semantics -- for
example, the removal of Python's "lists vs tuples" exceedingly
subtle distinction.  But mostly the score (as I keep it, with
simplicity a big plus and subtle, clever distinctions a notable
minus) is against Ruby (e.g., having both closed and half-open
intervals, with the notations a..b and a...b [anybody wants
to claim that it's _obvious_ which is which?-)], is silly --
IMHO, of course!).  Again, people who consider having a lot of
similar but subtly different things at the core of a language
a PLUS, rather than a MINUS, will of course count these "the
other way around" from how I count them:-).

Don't be misled by these comparisons into thinking the two
languages are _very_ different, mind you.  They aren't.  But
if I'm asked to compare "capelli d'angelo" to "spaghettini",
after pointing out that these two kinds of pasta are just
about undistinguishable to anybody and interchangeable in any
dish you might want to prepare, I would then inevitably have
to move into microscopic examination of how the lengths and
diameters imperceptibly differ, how the ends of the strands
are tapered in one case and not in the other, and so on -- to
try and explain why I, personally, would rather have capelli
d'angelo as the pasta in any kind of broth, but would prefer
spaghettini as the pastasciutta to go with suitable sauces for
such long thin pasta forms (olive oil, minced garlic, minced
red peppers, and finely ground anchovies, for example - but if
you sliced the garlic and peppers instead of mincing them, then
you should choose the sounder body of spaghetti rather than the
thinner evanescence of spaghettini, and would be well advised
to forego the achovies and add instead some fresh spring basil
[or even -- I'm a heretic...! -- light mint...] leaves -- at
the very last moment before serving the dish).  Ooops, sorry,
it shows that I'm traveling abroad and haven't had pasta for
a while, I guess.  But the analogy is still pretty good!-)

So, back to Python and Ruby, we come to the two biggies (in
terms of language proper -- leaving the libraries, and other
important ancillaries such as tools and environments, how to
embed/extend each language, etc, etc, out of it for now -- they
wouldn't apply to all IMPLEMENTATIONS of each language anyway,
e.g., Jython vs Classic Python being two implementations of
the Python language!):

1. Ruby's iterators and codeblocks vs Python's iterators
   and generators;

2. Ruby's TOTAL, unbridled "dynamicity", including the ability
   to "reopen" any existing class, including all built-in ones,
   and change its behavior at run-time -- vs Python's vast but
   _bounded_ dynamicity, which never changes the behavior of
   existing built-in classes and their instances.

Personally, I consider [1] a wash (the differences are so
deep that I could easily see people hating either approach
and revering the other, but on MY personal scales the pluses
and minuses just about even up); and [2] a crucial issue --
one that makes Ruby much more suitable for "tinkering", BUT
Python equally more suitable for use in large production
applications.  It's funny, in a way, because both languages
are so MUCH more dynamic than most others, that in the end
the key difference between them from my POV should hinge on
that -- that Ruby "goes to eleven" in this regard (the
reference here is to "Spinal Tap", of course).  In Ruby,
there are no limits to my creativity -- if I decide that
all string comparisons must become case-insensitive, _I CAN
DO THAT_!  I.e., I can dynamically alter the built-in string
class so that
    a = "Hello World"
    b = "hello world"
    if a == b
        print "equal!\n"
    else
        print "different!\n"
    end
WILL print "equal".  In python, there is NO way I can do
that.  For the purposes of metaprogramming, implementing
experimental frameworks, and the like, this amazing dynamic
ability of Ruby is _extremely_ appealing.  BUT -- if we're
talking about large applications, developed by many people
and maintained by even more, including all kinds of libraries
from diverse sources, and needing to go into production in
client sites... well, I don't WANT a language that is QUITE
so dynamic, thank you very much.  I loathe the very idea of
some library unwittingly breaking other unrelated ones that
rely on those strings being different -- that's the kind of
deep and deeply hidden "channel", between pieces of code that
LOOK separate and SHOULD BE separate, that spells d-e-a-t-h
in large-scale programming.  By letting any module affect the
behavior of any other "covertly", the ability to mutate the
semantics of built-in types is just a BAD idea for production
application programming, just as it's cool for tinkering.

If I had to use Ruby for such a large application, I would
try to rely on coding-style restrictions, lots of tests (to
be rerun whenever ANYTHING changes -- even what should be
totally unrelated...), and the like, to prohibit use of this
language feature.  But NOT having the feature in the first
place is even better, in my opinion -- just as Python itself
would be an even better language for application programming
if a certain number of built-ins could be "nailed down", so
I KNEW that, e.g., len("ciao") is 4 (rather than having to
worry subliminally about whether somebody's changed the
binding of name 'len' in the __builtins__ module...).  I do
hope that eventually Python does "nail down" its built-ins.

But the problem's minor, since rebinding built-ins is quite
a deprecated as well as a rare practice in Python.  In Ruby,
it strikes me as major -- just like the _too powerful_ macro
facilities of other languages (such as, say, Dylan) present
similar risks in my own opinion (I do hope that Python never
gets such a powerful macro system, no matter the allure of
"letting people define their own domain-specific little
languages embedded in the language itself" -- it would, IMHO,
impair Python's wonderful usefulness for application
programming, by presenting an "attractive nuisance" to the
would-be tinkerer who lurks in every programmer's heart...).

Alex 

Answer 29

In Ruby, when you import a file with require, all the things defined in that file will end up in your global namespace.

With Cargo you can "require libraries without cluttering your namespace".

# foo-1.0.0.rb
class Foo
  VERSION = "1.0.0"
end

# foo-2.0.0.rb
class Foo
  VERSION = "2.0.0"
end

>> Foo1 = import("foo-1.0.0")
>> Foo2 = import("foo-2.0.0")
>> Foo1::VERSION
=> "1.0.0"
>> Foo2::VERSION
=> "2.0.0"

Answer 30

At this stage, Python still has better unicode support