I am experimenting with the interactive interpreter environments of Python and Ruby and I ran into what seems to be a fundamental difference. However I may be doing something wrong in Python. Please comment and correct me if I am wrong
In both languages, you can start up the interactive interpreter ('python' and 'irb'), load source files and do stuff, like create objects and call their methods. When you want to change something, you can edit those same source files outside the environment and reload them from within the interactive environment. But, here is the difference: with Python, when you reload the source file (module in Python terms), it seems that your existing variables stay bound to the implementations from the old version of the module. In Ruby, after a reload, your existing variables point to the new implementation. At least, that is what happens with classes and their methods. This means that in Python, if you have an application built up interactively, with references to objects, data structures pointing to objects, etc., you would have to reconstruct that application to get the new implementation. With Ruby, when you load the new implementation, you get it immediately. here is a simple example: ------------------------------------------------------------------------------- Python interactive shell (python.exe) C:\home\dh0072\rq>python Python 2.4.2 (#67, Sep 28 2005, 12:41:11) [MSC v.1310 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. # load a local file b.py for test >>> import b # instantiate an object and call a method >>> x = b.B() >>> x.p() B # edit b.py offline to change method 'p' to do something different then reload >>> reload(b) >>> x.p() B # binding of variable 'x' IS NOT changed. points to old version >>> y = b.B() >>> y.p() BBBBB # new instance of 'b' points to new version >>> ------------------------------------------------------------------------------- Ruby interactive shell (irb.exe) C:\home\dh0072\rq>irb # load a local file b.py for test irb(main):001:0> load "b.rb" => true # instantiate an object and call a method irb(main):002:0> x = B.new => # irb(main):003:0> x.p B => nil # edit b.py offline to change method 'p' to do something different then reload irb(main):004:0> load "b.rb" => true irb(main):005:0> x.p BBBB => nil # binding of variable 'x' IS changed. points to new version irb(main):006:0> y = B.new => # irb(main):007:0> y.p BBBB => nil # new instance of 'b' points to new version -- http://mail.python.org/mailman/listinfo/python-list