Python Tree with unknown Height

Question

Assume I have 2 columns:

  OP_CODE      Additional Work
   a                 b
   a                 c
   a                 
   b                 d
   b                 e
   c                 
   d                 f
   d                 g
   d              
   e 
   f
   g

What I have to do is, I have to take a value from column OP_Code and get all corresponding values with Additional Work. Now Additional Work column values are my new OP_Codes. Then search for its corresponding Additional Works again. This process continues until I come across a blank cell for that particular column. The output of above table looks like below: https://i.stack.imgur.com/SycQM.png The thing is we dont know how many branches can a tree go on. Below is my code sample:

from anytree import Node, RenderTree
udo = Node("019201")


x = df_asra[df_asra.op_code == udo.name]


First_Level = {}
for i in range(0,len(x)):
    First_Level[i] = Node(x['Additional Work'].iloc[i], parent=udo)
for j in range(0,len(First_Level)):
    y = df_asra[df_asra['op_code'] == (First_Level[j]).name]
Second_Level = {}


while(y['Additional Work'].empty == False):


     for k in range(0,len(y)):
         Second_Level[k] = Node(y['Additional Work'].iloc[k], parent = First_Level[j])

     for l in range(0,len(Second_Level)):
         z = df_asra[df_asra['op_code'] == (Second_Level[l]).name]

     y = z
     First_Level = Second_Level





for pre, fill, node in RenderTree(udo):
     print("%s%s" % (pre, node.name))

Now I am getting output like this:

019201
├── 037061
│   ├── 015765
│   ├── 015795
│   │   ├── 013032
│   │   ├── 014270
│   │   ├── 015768
│   │   │   └── nan
│   │   └── nan
│   ├── nan
│   ├── nan
│   ├── nan
│   └── nan
├── nan
└── nan

Where Nan is blank column Now my problem is all branches are not in output. For example 014270 has further branches. It only runs for some parts. Plz Help