Add values of keys and sort it by occurrence of the keys in a list of dictionaries in Python

Question

I'm really new to Python and I'm stuck with the below problem that I need to solve. I've a log file from Apache Log as below:

[01/Aug/1995:00:54:59 -0400] "GET /images/opf-logo.gif HTTP/1.0" 200 32511
[01/Aug/1995:00:55:04 -0400] "GET /images/ksclogosmall.gif HTTP/1.0" 200 3635
[01/Aug/1995:00:55:06 -0400] "GET /images/ksclogosmall.gif HTTP/1.0" 403 298
[01/Aug/1995:00:55:09 -0400] "GET /images/ksclogosmall.gif HTTP/1.0" 200 3635
[01/Aug/1995:00:55:18 -0400] "GET /images/opf-logo.gif HTTP/1.0" 200 32511
[01/Aug/1995:00:56:52 -0400] "GET /images/ksclogosmall.gif HTTP/1.0" 200 3635

I've to return the 10 most requested objects and their cumulative bytes transferred. I need to include only GET requests with Successful (HTTP 2xx) responses.

So the above log would result into:

/images/ksclogosmall.gif 10905
/images/opf-logo.gif 65022

So far I've the following code:

import re
from collections import Counter, defaultdict
from operator import itemgetter
import itertools
import sys

log_file = "web.log"
pattern = re.compile(
      r'\[(?P<date>[^\[\]:]+):(?P<time>\d+:\d+:\d+) (?P<timezone>[\-+]?\d\d\d\d)\] '
      + r'"(?P<method>\w+) (?P<path>[\S]+) (?P<protocol>[^"]+)" (?P<status>\d+) (?P<bytes_xfd>-|\d+)')

dict_list = []

with open(log_file, "r") as f:
    for line in f.readlines():
        if re.search("GET", line) and re.search(r'HTTP/[\d.]+"\s[2]\d{2}', line):
            try:
                log_line_data = pattern.match(line)
                path = log_line_data["path"]
                bytes_transferred = int(log_line_data["bytes_xfd"])
                dict_list.append({path: bytes_transferred})
            except:
                print("Unexpected Error: ", sys.exc_info()[0])
                raise
    f.close()

print(dict_list)

This code prints the following list of dictionary.

[{'/images/opf-logo.gif': 32511}, 
{'/images/ksclogosmall.gif': 3635}, 
{'/images/ksclogosmall.gif': 3635}, 
{'/images/opf-logo.gif': 32511}, 
{'/images/ksclogosmall.gif': 3635}]

I don't know how to go about from here to get the result as:

/images/ksclogosmall.gif 10905
/images/opf-logo.gif 65022

This result is basically addition of values corresponding to similar keys sorted by number of times particular key occurred in a desc order.

Note: I tried using colllections.Counter with no avail, here I'd like to sort by the num of times the key occurred.

Any help would be appreciated.

Answer 1

You can use a collections.Counter and update it to add up the bytes transferred for each object:

from collections import Counter
c = Counter()
for d in dict_list:
    c.update(d)
occurrences=Counter([list(x.keys())[0] for x in dict_list])
sorted(c.items(), key=lambda x: occurrences[x[0]], reverse=True)

Output:

[('/images/ksclogosmall.gif', 10905), ('/images/opf-logo.gif', 65022)]