a script to load postgreSQL database into python

postgre-test.py

+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+"""
+Created on Fri Feb 28 15:19:55 2020
+
+@author: milena
+"""
+
+import psycopg2
+import sys
+import json
+import pandas as pd
+import numpy as np
+import matplotlib.pyplot as plt
+
+def get_var_data(data, var_name):
+    """
+    Return numpy array and pandas dataframe for selected variable from data fetched from the server.
+    """
+    var_data = np.empty([])
+    for row in data:
+        this_ev = json.loads(row[0])
+        this_ev_var = this_ev[var_name]
+        var_data = np.append(var_data, this_ev_var)
+
+    var_data_pd = pd.DataFrame(var_data)
+    return var_data, var_data_pd
+
+
+def get_var_names(data):
+    """
+    Get the list of variable names in messages.
+    """
+    return list(json.loads(data[0][0]).keys())
+
+
+#======== START HERE ========#
+#============================#
+
+# Connect to DB
+conn = psycopg2.connect(database="Lira", password='postgres',user="postgres", host="127.0.0.1")
+cursor = conn.cursor()
+print(conn.get_dsn_parameters(),'\n') # Print PostgreSQL Connection properties
+
+# Execute quory
+cursor.execute('SELECT message FROM "Measurements" WHERE "FK_MeasurementType"=2')
+data = cursor.fetchall()
+
+# Get variable names
+all_vars = get_var_names(data)
+
+# Test: Get one var
+acc_z_np, acc_z_pd = get_var_data(data, 'acc.xyz.z')
+plt.plot(acc_z_np)
+plt.title('acc.xyz.z')
+
+# Get data for all variables into np arrays and pd dataframes
+loaded_data = {}
+for var in all_vars:
+     var_np, var_pd = get_var_data(data, var)
+     loaded_data[var] = {'numpy':var_np, 'pandas':var_pd}
+
+