Python - very confused about method and while loop

Question

I have this method:

def is_active(self):
    if self.is_current_node():
        return True
    cur_children = self.get_children()
    while cur_children is not None:
        for child in cur_children:
            if child.is_current_node():
                return True
            raise Exception(child.display_name)
        cur_children = cur_children.get_children()
    return False

I put this method together and I put the raise Exception(child.display_name) to test out and "alert()" me to which child was being hit. The exception is never raised. You'd think that was because the function returned True on the if child.is_current_node() part. Well, if I replace the if part with this:

        for child in cur_children:
            if child.is_current_node():
                raise Exception(child.display_name)

It doesn't raise the exception still. If I do this however:

        for child in cur_children:
            raise Exception(child.display_name)

The exception is raised. I'm so confused. I'm sure this is something ridiculous but I was up till 2 and I can't think straight enough to wrap my tiny brain around this.

Answer 1

If the first child in the list .is_current_node(), then the exception will never be raised in your first snippet.

Everything you have for evidence is supporting the idea that either self.is_current_node() is always true, or the first scanned child .is_current_node(). Given the third code snippet, the latter seems to be the case.

EDIT: removing a misunderstanding (child != self) :/

Actually, I have to ask, what is this supposed to do? It looks vaguely like recursive tree-traversal, but it's not quite there. (the cur_children = cur_children.get_children() line in particular is a bit strange)

Answer 2

Some ideas:

cur_children = self._children while cur_children is not None: for child in cur_children: if child.is_current_node(): return True raise Exception(child.display_name) cur_children = cur_children._children

I assume that self._children contains multiple children: [A, B, C]

Then, on the first loop, it will take A . Let's assume that A has these children: [AA, AB, AC ].

Now, you do this: cur_children = cur_children._children . This means that now, instead of continuing with B from the inital [A, B, C] , it will continue with AA , and so on.

In this example, it will never reach B . Is this intended?

---

What does your is_current_node() contains? Probably you forgot to return a value, so the result is always None , and bool(None) == False .

---

Another idea: (recursion)

def is_active(self):

    def check_children(children):
        for child in children:
            if child.is_current_node():
                return True
            else:
                if children._children:
                    return check_children(children._children)
        return False

    if self.is_current_node():
        return True
    return check_children(children)

Answer 3

Maybe is_current_node always returns True and is_current_tab always returns False? I think more context is needed to give you an answer.

The only thing I can think of is that is_current_node changes state.