Question

Here is a simplified version of what I’m trying to do:

class a():
    Requirement = 0
    def func(self, oldlist, x):
        newlist = [None]*3
        newlist = oldlist
        newlist[x]  = b()
        print "Class a"
        g(newlist)


class b():
    Requirement = 1


def g(list):
    for i in range(3):
        if list[i].Requirement==0:
            list[i].func(list,i)

Initiallist=[None]*3
Initiallist[0]=a()
Initiallist[1]=b()
Initiallist[2]=a()
g(Initiallist)      

Instead of trying to express what I expect in words, I made some diagrams that express what in my mind should happen:

Which would imply that the function inside class a should be called 4 times. However, it only gets called 2 times, so it seems that this is happening:

I don’t understand why this is happening or how I should fix it.

Answer 1

Not sure, but I think your problem is this line:

newlist = oldlist

I guess you want to copy the list (and not altering oldlist), so you should simply use:

newlist = oldlist[:]

---

So changing func to

def func(self, oldlist, x):
    newlist = oldlist[:]
    newlist[x] = b()
    print "".join(x.__class__.__name__ for x in newlist)
    g(newlist)

prints

bba
bbb
abb
bbb