chochim - 1 year ago 68

Python Question

I am extremely sorry for being so naive. I am trying to implement a binary search tree in python (part of learning python in a way). I tried to google it, but I am unable to point out where I have faltered. What I am interested in knowing is not an implementation, but why my code is not working. Any help is really appreciated.

The code goes like as follows -

`class Node:`

rChild,lChild,data = None,None,None

def __init__(self,key):

self.rChild = None

self.lChild = None

self.data = key

class Tree:

root,size = None,0

def __init__(self):

self.root = None

self.size = 0

def insert(self,node,someNumber):

if node is None:

node = Node(someNumber)

else:

if node.data > someNumber:

self.insert(node.rchild,someNumber)

else:

self.insert(node.rchild, someNumber)

return

def main():

t = Tree()

t.root = Node(4)

t.root.rchild = Node(5)

print t.root.data #this works

print t.root.rchild.data #this works too

t = Tree()

t.insert(t.root,4)

t.insert(t.root,5)

print t.root.data #this fails

print t.root.rchild.data #this fails too

if __name__ == '__main__':

main()

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Answer Source

Here is a quick example of a binary insert:

```
class Node:
def __init__(self, val):
self.l_child = None
self.r_child = None
self.data = val
def binary_insert(root, node):
if root is None:
root = node
else:
if root.data > node.data:
if root.l_child is None:
root.l_child = node
else:
binary_insert(root.l_child, node)
else:
if root.r_child is None:
root.r_child = node
else:
binary_insert(root.r_child, node)
def in_order_print(root):
if not root:
return
in_order_print(root.l_child)
print root.data
in_order_print(root.r_child)
def pre_order_print(root):
if not root:
return
print root.data
pre_order_print(root.l_child)
pre_order_print(root.r_child)
```

```
r = Node(3)
binary_insert(r, Node(7))
binary_insert(r, Node(1))
binary_insert(r, Node(5))
```

```
3
/ \
1 7
/
5
```

```
print "in order:"
in_order_print(r)
print "pre order"
pre_order_print(r)
in order:
1
3
5
7
pre order
3
1
7
5
```

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