6.py

# Advent of code 2019 6 solution
# using anytree ([https://anytree.readthedocs.io/en/latest/](https://anytree.readthedocs.io/en/latest/))

from collections import defaultdict
from anytree import Node, Walker

orbit_map = defaultdict(list)
orbit_set = set()
orbit_tree = {}

# input_map is the input list provided
for item in input_map:
    parts = item.split(')')

    orbit_set.add(parts[0])
    orbit_set.add(parts[1])

    orbit_map[parts[0]].append(parts[1])

for i in orbit_set:
    orbit_tree[i] = Node(i) 

# construct tree - add children
for key, values in orbit_map.items():
    orbit_tree[key].children = [orbit_tree[i] for i in values]

# part 1
total = 0
for node in orbit_tree:
    total += orbit_tree[node].depth

print('Total orbits', total)

# part 2
you = orbit_tree['YOU']
san = orbit_tree['SAN']

w = Walker()
route = w.walk(you, san)

transfers = len(route[0]) + len(route[2]) - 2
print('Total transfers', transfers)