Problems with Matplotlib

[ihf]

I am trying to plot some data from an SQLITE db and I am having a problem with the data conversion:

import sqlite3
import time
import datetime

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.dates as mdates

conn = sqlite3.connect('acurite.sqlite')
c = conn.cursor()

sql = "SELECT * FROM acuriteHx"
graphArray = []

for row in c.execute(sql):
   startingInfo = str(row).replace(')','').replace('(','').replace('u\'','').replace("'","")
   splitInfo = startingInfo.split(',')
   graphArrayAppend = splitInfo[0] + ',' + splitInfo[2]
   graphArray.append(graphArrayAppend)
#print(graphArray)
datestamp, value = np.loadtxt(graphArray,delimiter=',', unpack=True,
                             converters={ 0: mdates.datestr2num('%Y-%m-%d %H:%M:%S')})

fig = plt.figure()

rect = fig.patch

sax1 = fig.add_subplot(1,1,1, axisbg='white')
plt.plot_date(x=datestamp, y=value, fmt='b-', label = 'value', linewidth=2)
plt.show()   ```

When run with Python2.7 it crashes Pythonista and when run with Python3 it gives:

Traceback (most recent call last):
 File "/private/var/mobile/Containers/Shared/AppGroup/4F06F35D-865B-4115-B827-BA053B3731EF/Pythonista3/Documents/sqliteplot.py", line 22, in <module>
   converters={ 0: mdates.datestr2num('%Y-%m-%d %H:%M:%S')})
 File "/var/containers/Bundle/Application/D78A900B-1E3B-4075-9CAB-F95408B28CD2/Pythonista3.app/Frameworks/Py3Kit.framework/pylib/site-packages/matplotlib/dates.py", line 283, in datestr2num
   dt = dateutil.parser.parse(d, default=default)
 File "/var/containers/Bundle/Application/D78A900B-1E3B-4075-9CAB-F95408B28CD2/Pythonista3.app/Frameworks/Py3Kit.framework/pylib/site-packages/dateutil/parser.py", line 749, in parse
   return DEFAULTPARSER.parse(timestr, **kwargs)
 File "/var/containers/Bundle/Application/D78A900B-1E3B-4075-9CAB-F95408B28CD2/Pythonista3.app/Frameworks/Py3Kit.framework/pylib/site-packages/dateutil/parser.py", line 311, in parse
   res, skipped_tokens = self._parse(timestr, **kwargs)
TypeError: 'NoneType' object is not iterable