Newick Format with Edge Weights

If you have already solved "Distances in Trees", then this problem will probably not take that long to complete. When I solved distances in trees, I used the Biopython module Phylo. The problem I had then was that the given trees did not contain any branch lengths, so I had to add this in the program. However in this problem the branch lengths are already included in the trees, so the new program is in fact even shorter than the original. You can find my new version of the code below and on my GitHub.

import sys
from Bio import Phylo
import io

f = open('rosalind_nkew.txt', 'r')
pairs = [i.split('\n') for i in f.read().strip().split('\n\n')]

for i, line in pairs:
    x, y = line.split()
    tree = Phylo.read(io.StringIO(i), 'newick')
    sys.stdout.write('%s' % round(tree.distance(x,y)) + ' ')
sys.stdout.write('\n')