If monkey patching is permitted in both Ruby and Python, why is it more controversial in Ruby?

Question

In many discussions I have heard about Ruby in which people have expressed their reservations about the language, the issue of monkey patching comes up as one of their primary c

Answer 1

The languages might permit it, but neither community condones the practice. Monkeypatching isn't condoned in either language, but you hear about it more often in Ruby because the form of open class it uses makes it very, very easy to monkeypatch a class and because of this, it's more acceptable in the Ruby community, but still frowned upon. Monkeypatching simply isn't as prevalent or as easy in Python, which is why you won't hear the same arguments against it in that community. Python does nothing that Ruby doesn't do to prevent the practice.

The reason you hear/read about it more often in Ruby is that this in Ruby:

class MyClass
  def foo
    puts "foo"
  end
end

class MyClass
  def bar
    puts "bar"
  end
end

will give you a class that contains two methods, foo and bar, whereas this in Python:

class MyClass:
    def foo(self):
        print "foo"

class MyClass:
    def bar(self):
        print "bar"

will leave you with a class that only contains the method bar, as redefinition of a class clobbers the previous definition completely. To monkeypatch in Python, you actually have to write this:

class MyClass:
    def foo(self):
        print "foo"

def bar(self):
    print "bar"
MyClass.bar = bar

which is harder than the Ruby version. That alone makes Ruby code much easier to monkeypatch than Python code.