If your class has __next__, it's an iterator. For iterators usually one just has __iter__ do return self.
#🔒 How to use `__iter__` and `__next__` for a BST
latent flame
(return iter(self) is invalid - it'll cause infinite recursion.)
hallow linden
return self doesnt work
i get this error
TypeError: 'Node' object is not iterable
do u wanna see my whole code?
hallow linden
class Node:
def __init__(self, value=None):
self.value = value
self.left = None
self.right = None
self.parent = None
class BinarySearchTree:
def __init__(self, name, root=None):
self.name = name
self.root = root
self.left_most = self.get_left_most()
def add_all(self, *items):
for item in items:
if self.root is None:
self.root = Node(item)
else:
current = Node(item)
while ((item < current.value) and (current.left is not None)) or (
(item > current.value) and (current.right is not None)):
if item > current.value:
current = current.right
elif item < current.value:
current = current.left
if item > current.value:
current.right = Node(item)
current.right.parent = current
if item < current.value:
current.left = Node(item)
current.left.parent = current
def __str__(self):
bst = "[" + self.name + "] ";
if self.root.value is not None:
bst += self.bst_print(self.root)
def bst_print(self, n):
s = ""
s += n.value
if n.left is not None:
s += " L:("
s += self.bst_print(n.left)
s += ")"
if n.right is not None:
s += " R:("
s += self.bst_print(n.right)
s += ")"
return s
def get_left_most(self):
temp = self.root
while temp.left is not None:
temp = temp.left
return temp
def __iter__(self):
return self
def __next__(self):
temp = self.left_most
if self.left_most.right is not None:
self.left_most = self.left_most.right
while self.left_most.left is not None:
self.left_most = self.left_most.left
return temp.value
else:
found = False
while not found:
if self.left_most.parent is None:
self.left_most = None
found = True
return temp.value
else:
if self.left_most.parent.left == self.left_most:
self.left_most = self.left_most.parent
found = True
return temp.value
self.left_most = self.left_most.parent
if __name__ == "__main__":
t1 = BinarySearchTree(name="Oak", root=Node())
t1.add_all(1, 0, 10, 2, 7)
for x in t1.root:
print(x)```
latent flame
t1 is a BinarySearchTree, which is iterable because it defines __iter__, but t1.root is a Node, which isn't.
hallow linden
so how do i fix this? i dont think we're supposed to define __iter__ inside Node itself
unless thats necessary
summer salmon
Perhaps you should not have a next method at all, but rather just an iter method
hallow linden
Perhaps you should not have a next method at all, but rather just an iter method
do i not need a next method?
summer salmon
If you have a next method, then the iter method should just return self, not iter(self) (which would be recursive anyways...)
latent flame
so how do i fix this? i dont think we're supposed to define ``__iter__`` inside ...
I can't tell you how to fix this because I don't know what you want to achieve. If it's the BST that should be iterable, iterate over it rather than its root node - like for x in t1:
hallow linden
i realize i think the teacher made a typo
because t1.root makes no sense
if i do for x in t1:
print(x)
then it works slightly better but im still getting error
is there a way to make a variable outside of a constructor in a python class that can be updated by other methods?
summer salmon
hallow linden
cuz like the error im getting now has to do with getting the leftMost aka the very left of the tree
and in my implementation
def __init__(self, name, root=None):
self.name = name
self.root = root
self.left_most = self.get_left_most()```i did this
which get_left_most
basically finds it given self.root
but
i dont think thats working as intended
bc it says that left most is None TYpe
from the start
no matter what
wait hmm
yeah
thats so weird
class Node:
def __init__(self, value=None):
self.value = value
self.left = None
self.right = None
self.parent = None
class BinarySearchTree:
def __init__(self, name, root=None):
self.name = name
self.root = root
self.left_most = root
def add_all(self, *items):
for item in items:
if self.root.value is None:
self.root = Node(item)
self.left_most = self.root
else:
current = Node(item)
while ((item < current.value) and (current.left is not None)) or (
(item > current.value) and (current.right is not None)):
if item > current.value:
current = current.right
elif item < current.value:
current = current.left
if item > current.value:
current.right = Node(item)
current.right.parent = current
if item < current.value:
current.left = Node(item)
current.left.parent = current
if item < self.left_most.value:
self.left_most = current
def __str__(self):
bst = "[" + self.name + "] ";
if self.root.value is not None:
bst += self.bst_print(self.root)
def bst_print(self, n):
s = ""
s += n.value
if n.left is not None:
s += " L:("
s += self.bst_print(n.left)
s += ")"
if n.right is not None:
s += " R:("
s += self.bst_print(n.right)
s += ")"
return s
def __iter__(self):
return self``` def __next__(self):
temp = self.left_most
print(temp.value)
if self.left_most.right is not None:
self.left_most = self.left_most.right
while self.left_most.left is not None:
self.left_most = self.left_most.left
return temp.value
else:
found = False
while not found:
if self.left_most.parent is None:
self.left_most = None
found = True
return temp.value
else:
if self.left_most.parent.left == self.left_most:
self.left_most = self.left_most.parent
found = True
return temp.value
self.left_most = self.left_most.parent
if __name__ == "__main__":
t1 = BinarySearchTree(name="Oak", root=Node())
t1.add_all(1, 0, 10, 2, 7)
for x in t1:
print(x)
this is my new code
and i get the error
the print is just for me to check the values of temp
for debugging
but how is it none type if its the left_most value
which is updated during add_all
hallow linden
i fixed it but ty yall
fallow nest