title: Can't extract data from list of dictionaries, 'NoneType' object is not subscript
body: <p>I have a pickle file <code>AQM_kath.pkl</code> that is two sensor locations and their data in a dictionary.</p>
  <pre><code>len(AQM_kath)
  &gt;&gt;&gt; 2
  
  len(AQM_kath[0])
  &gt;&gt;&gt; 1011
  
  len(AQM_kath[1])
  &gt;&gt;&gt; 1026
  </code></pre>
  <p>Each of the entries in the respective lists is a dictionary entry (sensor 1 has 1011 entries, sensor 2 has 1026) with several keys. I am trying to run through both sensor locations (AQM_kath[0] and AQM_kath[1]) and compile all of the data entries of a specific key into 1 list. The included keys are <code>Image</code>, <code>Date</code>, <code>Time</code>, and <code>Temp</code>. Here is what i have tried so far for temperature, my end goal is a 2037 length list of temperatures:</p>
  <pre><code>import pickle as pkl
  import numpy as np
  
  temp =[]
  with open('/work/AQM_kath.pkl', 'rb') as fp:
      for station in tqdm(pkl.load(fp)):
          for data_point in station:
              temp.append(data_point['Temp'])
  </code></pre>
  <p>However i get the error</p>
  <pre><code>TypeError                                 Traceback (most recent call last)
  &lt;ipython-input-68-41f4e4b6f854&gt; in &lt;module&gt;
        3     for station in tqdm(pkl.load(fp), position=0, leave=True):
        4         for data_point in station:
  ----&gt; 5             temp.append(data_point['Temp'])
  
  TypeError: 'NoneType' object is not subscriptable
  </code></pre>
  <p>It works for the first 10 entries, but then spits out this error. Not sure what i'm missing here, any help appreciated!</p>