a=[1,2,4]
p a.object_id
b=a
p b.object_id
b[1]=a[0]
p a.object_id,b.object_id
b[0]=a[1]
p a.object_id,b.object_id

538408680
538408680
538408680
538408680
538408680
538408680

同じかどうかはobject_idで調べること
> b=a はずっと効いているわけではない
じゃあ「どこで」「どういう理屈で」切れるん？