def generate_recommendations_for_one_user(user_download_history, recommendations, one_user_id):
all_app_id = recommendations.keys()
recommended_app_list = []
sim_score = []
for app in user_download_history[ one_user_id ]:
if app in all_app_id:
for one_sim_app in recommendations[app]:
recommended_app_list.append(one_sim_app[0])
sim_score.append(one_sim_app[1])
sorted_list = [x for (y,x) in sorted(zip(sim_score, recommended_app_list), key=lambda pair: pair[0], reverse = True)]
DataService.update_user_download_history({'user_id':one_user_id}, {'$set':{"recommended_apps":sorted_list}})
return
