Comments on: Ruby style method injection in Python

By: Nicolas

Nicolas — Thu, 30 Apr 2009 23:28:33 +0000

You’d get unbound method if you tried to call the method as if it were a static method, i.e. straight off the class … in this case Foo.bar().

if that is indeed what you wanted to do… you have to make it a class method … (by either @classmethod in python 2.4+ or simply bar = classmethod(bar) after its definition in the class)

By: Michal Vyskocil

Michal Vyskocil — Thu, 30 Apr 2009 09:48:10 +0000

I thought I got something like unbound method error in this case, but your example runs well.

By: Joachim Werner

Joachim Werner — Thu, 30 Apr 2009 08:21:28 +0000

class Foo:
def foo(self):
return ‘foo’

aFoo = Foo()
aFoo.foo()

def bar(self):
return ‘bar’

Foo.bar = bar

aFoo.bar()

By: Joachim Werner

Joachim Werner — Thu, 30 Apr 2009 08:19:18 +0000

class Foo:
def foo(self):
return ‘foo’

aFoo = Foo()
aFoo.foo()

def bar(self):
return ‘bar’

Foo.bar = bar

aFoo.bar()

By: Joachim Werner

Joachim Werner — Thu, 30 Apr 2009 08:15:19 +0000

Another try. Seems like the code tag is not what makes my code snippet show up as code:

By: Joachim Werner

Joachim Werner — Thu, 30 Apr 2009 08:10:18 +0000

What about this?

class Foo: def foo(self): return 'foo'


aFoo = Foo()

aFoo.foo()
def bar(self):

    return 'bar'
Foo.bar = bar

aFoo.bar()

It does just the same as the initial Ruby example, but IMHO makes it much more obvious that I’m adding a new method to an existing class.

By: Simon Davy

Simon Davy — Thu, 30 Apr 2009 07:25:35 +0000

hmm – both languages allow excactly the same thing with different syntax – python is more explicit, ruby is more implcit, as per normal

By: Michal Vyskocil

Michal Vyskocil — Thu, 30 Apr 2009 07:21:36 +0000

Interesting, I didn’t tested it with class (and static) methods, because I don’t need it, so thanks for the link.

By: Michal Vyskocil

Michal Vyskocil — Thu, 30 Apr 2009 07:20:20 +0000

I don’t think that this is a best example, because this implicit behavior of open classes is against Python design rules. Better example should be in method naming, when method? returns boolean and method! modify an instance. In Python is obviously not clear which method do what. So in this case is Ruby more “pythonic” (means explicit) than Python itself :).

By: Michal Vyskocil

Michal Vyskocil — Thu, 30 Apr 2009 07:06:47 +0000

I like Python philosophy “explicit is better than implicit”. So those implicit adding of new methods which looks like normal class declaration* is uncommon. At least for those of us which are not familiar with Ruby. And I am, because that was my first “hello world” in Ruby :-).

* Yes, I know that definitions/declaration does not make a sense in dynamic languages, but I’m still thinking in those sentences.