use extra variable instead of post['category'] directly

scrape.py

@@ -152,8 +152,9 @@ async def main():
             # scrape all blog posts and process them
             blog = get_blog()
             for post in blog:
+                category = post['category']
                 # check if post url is in cache and matches our category
-                if post['category'] in category_list and post['url'] not in cache[post['category']]:
+                if category in category_list and post['url'] not in cache[category]:
                     # post url not found in cache
                     # announce new post to matrix rooms
                     print('new post: '+post['url'])
@@ -173,7 +174,7 @@ async def main():
                                                    content=content)
 
                     # add url to cache
-                    cache[post['category']] += [post['url']]
+                    cache[category] += [post['url']]
 
                 else:
                     # no new posts found