python - Multiple different versions of similar apps in one project -

i need improve architecture of site i've built. want achieve within single django project following:

• i want site comes in several versions (one per year), such each version has set of apps related version.

• i want keep old versions of site , state of apps in version, still being able add/change/remove apps other version. is, apps may different across versions (models, methods, admin, templates, basically).

• i want each app belongs version have data version only. app1 on version 2012 should have 1 database table, , app1 on version 2013 should have another, if same.

it this:

site.com/2012     app1_v1     app2_v1  site.com/2013     app1_v1     app2_v2 (maybe added fields or methods, changed templates)  site.com/2014     app1_v2     app2_v2     app3_v1 

my current solution rather horrible. when new version of site launched, copy-paste earlier app , have old app is, , adding/modifying new version of app. but, add more apps , more versions come, stupid amount of apps , feels bad design.

how can achieve in django in better way? or @ least, how can structure in better way? think having base model each app, each version inherits from, still makes lot of apps.

as example of app have, may this:

app name: app_v1_2012

model

class bag(models.model)     name = models.charfield()  class item(models.model)     name = models.charfield()     in_bag = models.foreignkey(bag) 

view

class indexview(generic.listview):     model = bag     template_name = 'sometemplate_2012.html' 

app name: app_v1_2013

model

class bag(models.model)     name = models.charfield()  class item(models.model)     name = models.charfield()     in_bag = models.foreignkey(bag) 

view

class indexview(generic.listview):     model = bag     template_name = 'sometemplate_2013.html' 

app name: app_v2_2014

model

class bag(models.model)     bag_name = models.charfield()     owner = models.foreignkey(user)  class item(models.model)     name = models.charfield()     in_bag = models.foreignkey(bag) 

view

class indexview(generic.listview):     model = bag     template_name = 'sometemplate_2014.html' 

as can see, biggest problem violation of dry principle. copy-pasted, it's same information.

why don't import models , views previous apps, if library functions? can inherit other classes , add methods , attributes, or override them when necessary. python has lots of oop tools these kinds of situations.