Calculate differences between two browsercompat issues counts, and format as MarkDown

diff_issues.py

#!/usr/bin/env python
from __future__ import print_function
import csv
import sys

if len(sys.argv) != 3:
    print("Usage: {} older_count.csv newer_count.csv".format(sys.argv[0]))
    sys.exit(0)


def get_data(filename):
    data = []
    with open(filename, 'rb') as older_file:
        reader = csv.reader(older_file)
        first = True
        for count, slug in reader:
            if first:
                first = False
            else:

                data.append((int(count), slug))
    return data

older = get_data(sys.argv[1])
newer = get_data(sys.argv[2])

by_count = [slug for count, slug in sorted(older, reverse=True)]
older_by_slug = dict((slug, count) for count, slug in older)
newer_by_slug = dict((slug, count) for count, slug in newer)

ordered = []
slug_out = set()
for slug in by_count:
    old_value = older_by_slug[slug]
    new_value = newer_by_slug.get(slug, 0)
    ordered.append((slug, old_value, new_value))
    slug_out.add(slug)

for slug, new_value in newer_by_slug.items():
    if slug not in slug_out:
        old_value = 0
        ordered.append((slug, old_value, new_value))

max_len = max([len(x) for x, _, __ in ordered])

print("{0:^{1}} | Old Count | New Count".format("Issue Slug", max_len))
print("{}-|-----------|----------".format("-" * max_len))
old_total = sum(count for count in older_by_slug.values())
new_total = sum(count for count in newer_by_slug.values())
print("{0:<{1}} | {2:>9} | {3:>9}".format(
    '**Total**', max_len, old_total, new_total))
for slug, oldc, newc in ordered:
    print("{0:<{1}} | {2:>9} | {3:>9}".format(slug, max_len, oldc, newc))