Is there anyway to print a tree vertically in Python? Like a real tree

Question

I'm trying to print a tree, the problem is that I can't find any other way than printing it like this:

1
|__2
   |__3
      |__33
   |__4
|__22

But is there any way to print it like this:

Here is my code:

class treeNode:

    def __init__(self,data):
        self.data = data
        self.children = []
        self.parent = None
        self.nextSibling = None
        self.level = 0
        self.prevSibling = None

Here, I created a class for the tree nodes, I know that the code is bad but I am still a beginner and I will improve it in the future. I used lists to store children and linked lists to sort siblings because it will be useful later when trying to print the actual tree.

    def add_children(self,*child):
        for i in child:
            i.parent = self
            self.children.append(i)
            if len(self.children) > 1:
                self.children[-2].nextSibling = i

class Tree:

    def __init__(self,root:treeNode):
        self.root = root
        self.depth = 0

    def print_tree(self):
        print(self.root.data)
        kid = self.root.children[0]
        while (kid != self.root):
            kid.level_func()
            print("  " * (kid.level - 1) * 2 + "|" + "__",kid.data)
            if len(kid.children) == 0:
                while kid.parent:
                    if kid.nextSibling:
                        kid = kid.nextSibling
                        break
                    else:
                        kid = kid.parent
            else:
                kid = kid.children[0]

The way I printed the tree is in this order: print current node, go to children if the current node has any kids, if not go to the current node 's parent 's next sibling and it will continue like that until it reaches the root.

Thanks in advance :)

Before starting to code you should also know what the output should be in more complicated situations, e. g. if 22 has two children, too. — Michael Butscher, Oct 25 '21 at 19:36
@MichaelButscher yes i know, but here i am talking about binary trees — Zakaria Ayadi, Oct 25 '21 at 19:37
In a binary tree each node can have zero to two children therefore "22" can also have two ones. — Michael Butscher, Oct 25 '21 at 19:39
"yes i know, i shouldnt have used 2 data structures" huh? What do you mean? — juanpa.arrivillaga, Oct 25 '21 at 19:40
@MichaelButscher so it has something to to do with the width of the tree? — Zakaria Ayadi, Oct 25 '21 at 19:42
@juanpa.arrivillaga i mean in the treenode class, i used both lists and linked lists data structures — Zakaria Ayadi, Oct 25 '21 at 19:42
@ZakariaAyadi Yes. "2" and "22" would need more distance between each other for my example. This would in turn need a way to show the connection between nodes with some more "ascii art". You must first decide how it should look like before you can code it. — Michael Butscher, Oct 25 '21 at 19:49
thank you @MichaelButscher, i'll try to code firstl a method that finds the width of the tree, and then i'll try to print it in that way — Zakaria Ayadi, Oct 25 '21 at 19:51
I would suggest using a cleaner data structure before investing in coding such a print function. — trincot, Oct 25 '21 at 20:43
See the printBTree function here: https://stackoverflow.com/a/49844237/5237560 — Alain T., Oct 25 '21 at 20:50

Alain T. · Answer 1 · 2021-10-25T21:16:30.127

If your tree is a binary tree, the second form can be obtained using the printBTree function here

for example:

              80
          ___/  \___
        50          90
     __/  \__      /
   10        60  85
  /  \      /  \
 5    30  55    70
        \
         35

You could try to make a variant of it for a tree with multiple children but you will quickly run out of horizontal space.

for those trees, the indented format is preferable, although you could make it look a little better:

def printTree(node,nodeInfo,indent=""):
    label,children = nodeInfo(node)
    print(indent[:-3] + "|_ "*bool(indent) + str(label))
    for more,child in enumerate(children,1-len(children)):
        childIndent = "|  " if more else "   "
        printTree(child,nodeInfo,indent+childIndent)

Usage:

T = {'data': 1, 'children':
        [ { 'data':2, 'children':
            [ {'data':6 }, {'data':7} ]},
          {'data':3},
          {'data':4},
          {'data':5, 'children':
           [{'data':10}]}
        ]
     }

printTree(T,lambda d:(d['data'],d.get('children',[])))

1
|_ 2
|  |_ 6
|  |_ 7
|_ 3
|_ 4
|_ 5
   |_ 10

You could use printTree with your treeNode class like this:

printTree(myTree.root,lambda n:(n.data,n.children))

Is there anyway to print a tree vertically in Python? Like a real tree

1 Answers1