Implement processing of images on multiple threads at once

imgrate.py

@@ -51,9 +51,11 @@ if __name__ == '__main__':
     from os import remove
     from sys import exit
     from signal import signal, SIGINT
+    from multiprocessing import Pool, cpu_count
 
     signal(SIGINT, lambda a, b: exit('\nExiting!'))
 
+
     def parse_arguments():
         ap = ArgumentParser(description='Find the best quality one among similar images.'
                                         'Note: image dimensions should match!')
@@ -65,21 +67,38 @@ if __name__ == '__main__':
 
 
     def run(args):
-        try:
+        if not hasattr(imgrate, args.method):
-            ratings = {image: getattr(imgrate(image), args.method) for image in args.images}
-        except AttributeError:
             exit('Invalid --method option!')
+
+        ratings = calculate_all_ratings(args.images, args.method)
         maximum = max(ratings, key=ratings.get)
 
-        for rating in ratings.keys():
+        fancy_print_ratings(ratings, args.quiet, maximum)
-            if args.quiet:
-                print(ratings[rating])
-            else:
-                maxmark = '*' if rating == maximum and len(ratings) > 1 else ' '
-                print('{}imgrate("{}") = {}'.format(maxmark, rating, ratings[rating]))
 
         if args.delete:
             [remove(image) for image in ratings if image != maximum]
 
 
+    def calculate_all_ratings(images, method):
+        ratings = []
+        with Pool(processes=cpu_count()) as pool:
+            for image in images:
+                ratings.append((image, pool.apply_async(calculate_rating, (image, method))))
+
+            return {image: promise.get() for image, promise in ratings}
+
+
+    def calculate_rating(image, method):
+        return getattr(imgrate(image), method)
+
+
+    def fancy_print_ratings(ratings, quiet, maximum):
+        for rating in ratings.keys():
+            if quiet:
+                print(ratings[rating])
+            else:
+                maxmark = '*' if rating == maximum and len(ratings) > 1 else ' '
+                print('{}imgrate("{}") = {}'.format(maxmark, rating, ratings[rating]))
+
+
     run(parse_arguments())