Print out a count of focal lengths from canon raw image files

focal_length.py

#!/usr/bin/env python
# Author: Justin Lintz
# usage: ./focal_length dir
# Requiresments: dcraw http://www.cybercom.net/~dcoffin/dcraw/
import os
import sys
from subprocess import Popen, PIPE
from operator import itemgetter

focals = {}
DCRAW='/path/to/dcraw'

def process_files(filelist):
    for filename in filelist:
        p = Popen([DCRAW,'-i','-v',filename],stdout=PIPE)
        for line in p.stdout:
            if line.startswith('Focal'): 
                length = line.split(':')[1].strip()
                focal = length[:-2]
                if focal in focals : 
                    focals[focal] = focals[focal] + 1
                else:
                    focals[focal] = 1
        
def get_raw_files(path):
    file_list = []
    for root,dirs,files in os.walk(path):
        for filename in files:
            if filename.endswith('CR2'):
                file_list.append(os.path.join(root,filename))
    return file_list

def main():
    files = get_raw_files(sys.argv[1])
    print 'Total pics to process: %d' % len(files)
    process_files(files)
    sorted_list = sorted(focals.items(),key=itemgetter(1),reverse=True)
    for length,count in sorted_list:
        print 'Length: %s , Count: %d' % (length,count) 
    return 0
    
if __name__ == "__main__":
    main()