better database alias object

photoapp/api.py

@@ -25,7 +25,7 @@ class PhotosApiV1(object):
 
     @cherrypy.expose
     def index(self):
-        yield f"<plaintext>hello, this is the api. my database is: {db()}\n"
+        yield f"<plaintext>hello, this is the api. my database is: {db}\n"
 
     @cherrypy.expose
     def upload(self, files, meta):
@@ -34,7 +34,7 @@ class PhotosApiV1(object):
     @cherrypy.expose
     @cherrypy.tools.json_out()
     def byhash(self, sha):
-        f = db().query(Photo).filter(Photo.hash == sha).first()
+        f = db.query(Photo).filter(Photo.hash == sha).first()
         if not f:
             raise cherrypy.HTTPError(404)
         return f.to_json()
@@ -42,14 +42,14 @@ class PhotosApiV1(object):
     @cherrypy.expose
     @cherrypy.tools.json_out()
     def set(self, uuid):
-        s = db().query(PhotoSet).filter(PhotoSet.uuid == uuid).first()
+        s = db.query(PhotoSet).filter(PhotoSet.uuid == uuid).first()
         if not s:
             raise cherrypy.HTTPError(404)
         return s.to_json()
 
     @cherrypy.expose
     def download(self, uuid):
-        f = db().query(Photo).filter(Photo.uuid == uuid).first()
+        f = db.query(Photo).filter(Photo.uuid == uuid).first()
         if not f:
             raise cherrypy.HTTPError(404)
         return cherrypy.lib.static.serve_file(os.path.abspath(os.path.join("./library", f.path)),
@@ -59,16 +59,16 @@ class PhotosApiV1(object):
     @cherrypy.tools.json_out()
     def user(self, username=None, password_hash=None):
         if username is None:  # list all users
-            return [u.to_json() for u in db().query(User).all()]
+            return [u.to_json() for u in db.query(User).all()]
         elif username and cherrypy.request.method == "DELETE":  # delete user
-            u = db().query(User).filter(User.name == username).first()
+            u = db.query(User).filter(User.name == username).first()
             if not u:
                 raise cherrypy.HTTPError(404)
-            db().delete(u)
+            db.delete(u)
         elif username and password_hash:  # create/update user
-            u = db().query(User).filter(User.name == username).first()
+            u = db.query(User).filter(User.name == username).first()
             if u:
                 u.password = password_hash
             else:
-                db().add(User(name=username, password=password_hash))
+                db.add(User(name=username, password=password_hash))
         return "ok"

photoapp/dbutils.py

@@ -7,8 +7,19 @@ from sqlalchemy.ext.declarative import declarative_base
 Base = declarative_base()
 
 
-def db():
+class DbAlias(object):
-    return cherrypy.request.db
+    """
+    This provides a shorter alias for the cherrypy.request.db object, which is a database session created bound to the
+    current request. Since the `db` attribute doesn't exist until a request is received, we cannot simply reference it
+    with another variable.
+
+    And instance of this class acts as an object proxy to the database object in cherrypy.request.db.
+    """
+    def __getattr__(self, attr):
+        return getattr(cherrypy.request.db, attr)
+
+
+db = DbAlias()
 
 
 class SAEnginePlugin(plugins.SimplePlugin):