Reading lines from text and converting it into Python nested dictionary

Question

So i have the below text as an input file:

A B 1
A C 2
B C 1
B D 3
B E 2
C D 1
C E 2
D E 4
D F 3
E F 3

and i want to store all these values in a nested dictionary in python:

{ 'A': {'B': 1, 'C': 2},
'B': {'C': 1, 'D': 3, 'E': 2},
'C': {'D': 1, 'E': 2},
'D': {'E': 4, 'F': 3},
'E': {'F': 3} }

This is my code which is reading an input file and trying to convert it into a nested dictionary

inputfile = open("input.txt", "r")
lines = inputfile.readlines()
edges = []
for line in lines:
    edges.append(line.split())
d = {}
nn={}

for i in edges:
    nn.update({i[1]:i[2]})
    d[i[0]] = nn
    index+=1

print(d)

This is my incorrect output

{'A': {'B': '1', 'C': '1', 'D': '1', 'E': '4', 'F': '3'}, 'B': {'B': '1', 'C': '1', 'D': '1', 'E': '4', 'F': '3'}, 'C': {'B': '1', 'C': '1', 'D': '1', 'E': '4', 'F': '3'}, 'D': {'B': '1', 'C': '1', 'D': '1', 'E': '4', 'F': '3'}, 'E': {'B': '1', 'C': '1', 'D': '1', 'E': '4', 'F': '3'}}

I am looking for a correct if else condition which will update the dict items when the key is same and append if it is different. Thanks in advance.

dawg · Accepted Answer · 2018-11-11 00:30:47Z

1

You can do:

di={}
with open(fn) as f_in:
    for line in f_in:
        li=line.split()
        di.setdefault(li[0],{})[li[1]]=li[2]

>>> di
{'A': {'B': '1', 'C': '2'}, 'B': {'C': '1', 'D': '3', 'E': '2'}, 'C': {'D': '1', 'E': '2'}, 'D': {'E': '4', 'F': '3'}, 'E': {'F': '3'}}

answered Nov 11, 2018 at 0:30

dawg

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Comments

Ajax1234 · Accepted Answer · 2018-11-11 00:37:04Z

0

You can use recursion with collections.defaultdict:

import collections
def group(d):
  _d = collections.defaultdict(list)
  for a, *b in d:
    _d[a].append(b)
  return {a:group(b) if len(b) > 1 else dict(b) if len(b[0]) > 1 else b[0][0] for a, b in _d.items()}

content = [i.strip('\n').split() for i in open('filename.txt')]
final_result = group(content)

Output:

{'A': {'B': '1', 'C': '2'}, 'B': {'C': '1', 'D': '3', 'E': '2'}, 'C': {'D': '1', 'E': '2'}, 'D': {'E': '4', 'F': '3'}, 'E': {'F': '3'}}

This will also work on larger input samples:

s = """
  A B C D
  A C D E
  A H I F
  B D T G
  B F E H
  B U F A
  """
content = [i.split() for i in filter(None, s.split('\n'))]
print(group(content))

Output:

{'A': {'B': {'C': 'D'}, 'C': {'D': 'E'}, 'H': {'I': 'F'}}, 'B': {'D': {'T': 'G'}, 'F': {'E': 'H'}, 'U': {'F': 'A'}}}

edited Nov 11, 2018 at 0:37

answered Nov 11, 2018 at 0:27

Ajax1234

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1 Comment

Sahil Sood Over a year ago

Thank you so much for the quick response and a very informative answer. I am still learning Python basics and this really helped me to understand the concept of recursion.

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