You need to pass an object identifier (pk or slug) so your views know which object they’re operating on.
Just to take an example from your urls.py:
url(r'^facture/ajouter/$', Facture_Creer.as_view(), name="facture_creer"),
url(r'^facture/modifier/(?P<pk>\d+)/$', Facture_Update.as_view(), name="facture_update"),
See how the second one has (?P<pk>\d+)/? That is passing a pk to the UpdateView so it knows which object to use. Thus if you go to facture/modifier/5/, then the UpdateView will modify object with pk of 5.
If you don’t want to pass a pk or slug in your url, you’ll need to override the get_object() method and get your object another way. Url here.