Perl/Python/Ruby common backend (Parrot, can Ruby play too?)

Andrew Dalke dalke at acm.org
Tue Aug 7 17:10:40 CEST 2001


[c.l.ruby removed, for obvious reasons]

Alex Martelli wrote:
>If you want existing instances to NOT be changed, in Python,
>just leave the existing class object alone and build a new one.

Right, but she wanted a way to update existing class
definitions *and* existing instances.

>E.g,
>class theclass(theclass): pass

Cute :) but it doesn't update existing instances.

class Spam:
  def eat(self): print "yum"

spam = Spam()
spam.eat()

# Oops, I don't like spam, so let me change that
 ... code to update Spam, as perhaps
def Spam.eat(self): print "yech"
 ...

# Uses the old 'spam'
spam.eat()

This should print
yum
yech

and using a 'class Spam(Spam): def eat(self): print "yech"'
is not enough.

BTW, I wish to stress that I am not pushing this to be added to
Python.  I am not sure enough about the use case on what this
is based to tell if this is a useful solution.  (Eg, it could
be that reloading a module in a way that changes class definitions
in-place rather than replacing them is more appropriate.)

Still, I know in interactive mode that I've made a lot of
mistakes in making a class, so perhaps something like this
would be useful.  (Given the chance for abuse, I don't think
it is useful.)

                    Andrew
                    dalke at dalkescientific.com






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