Store cadence values in database

db.py

@@ -0,0 +1,36 @@
+import os
+import psycopg2
+from psycopg2.extras import RealDictCursor
+from urllib.parse import urlparse
+
+
+class DataBase():
+    def __init__(self, app):
+        db_url = urlparse(os.environ['DATABASE_URL'])
+
+        self.conn = psycopg2.connect(
+            database=db_url.path[1:],
+            user=db_url.username,
+            password=db_url.password,
+            host=db_url.hostname,
+            port=db_url.port
+        )
+
+    def execute(self, query, args=(), one=False, commit=False):
+        cur = self.conn.cursor(cursor_factory=RealDictCursor)
+        cur.execute(query, args)
+        rv = None
+        if cur.description is not None:
+            rv = cur.fetchall()
+        if commit:
+            try:
+                self.conn.commit()
+            except:
+                self.conn.rollback()
+        cur.close()
+
+        return (rv[0] if rv else None) if one else rv
+
+    def insert_cadence(self, rpm, device_id):
+        self.execute('INSERT INTO cadence (rpm, device_id) VALUES (%s)',
+                     [rpm, device_id], commit=True, one=True)