A tag counting script with comments

tag_counts.py

import sys
import json
import codecs
from collections import defaultdict

# This line will fix your unicode printing woes... still getting the hang of
# using codecs for everything, but it's important
sys.stdout = codecs.getwriter("utf8")(sys.stdout)

# collections.Counter was introduced in 2.7 -- this is 2.6 compatible
# this is the real goodness
tag_counts = defaultdict(int)
 
# Using sys.argv[1] allows you to use this on other files in the future without
# modifying the script
with open(sys.argv[1]) as f:
    # Using `for line in file` syntax allows you to process each line of the
    # data without loading it all into memory at once
    for line in f:
        # Try/Catch for the first brackets which are not considered "proper" JSON
        try:
            # Stripping the whitespace and commas is a decent bit cleaner here
            # Also, this is really a device_info dictionary, not JsonFormat
            device_info = json.loads(line.strip().strip(','))
        # Always catch Exception (or more specific) so that KeyboardInterrupt
        # (ctrl + C) will still stop the program
        # Also, keep your try blocks as small as possible
        except Exception:
            continue

        # It's tags... so name it what it is
        # Man it is dumb that gimme outputs the tags in this format... sorry
        # !meaculpa
        tags = eval(device_info["tags"])

        # tags could be None
        if not tags:
            continue
        
        for tag in tags:
            # Using the magic/beauty of defaultdict/counter here
            # defaultdict(int) is essentially the same as Counter()
            # read more here:
            # http://docs.python.org/2/library/collections.html#counter-objects
            tag_counts[tag] += 1


# I prefer to print to stdout in my scripts, since you can just 
# python my_script.py input.txt > out.txt
# and get more or less the same result as writing to a file which gives me 
# added flexibility
for tag, count in tag_counts.iteritems():
    print tag, "--", count



# The rest of the code is an example that I don't want to actually execute, so
# I'm exiting early.  Don't actually need to use sys.exit(0).
sys.exit(0)



# If you really want to write to a file, you could use something like this...

# Open 2nd file provided on the command line in "write binary" mode
# You don't need to use codecs.open(sys.argv[2], 'wb', 'utf8') but it would be safer
with open(sys.argv[2], 'wb') as f:
    for tag, count in tag_counts.iteritems():
        f.write(u"{0} -- {1}".format(tag, count))