title: AttributeError: 'Series' object has no attribute 'sqrt'
body: <p>I am working with some datasets that I have imported from EXCEL and converted into lists:</p>
  
  <pre><code>import pandas as pd
  import numpy as np
  
  datfrms = []
  for i in xls.sheet_names:                                       
      df = pd.read_excel(xls, i)
      datfrms.append(df) 
  
  data_a = []
  data_b = []
  data_c = []
  
  for dfs in datfrms:
      data_a.append(dfs.loc[:,'data_a'])
      data_b.append(dfs.loc[:,'data_b'])
      data_c.append(dfs.loc[:,'data_c'])
  </code></pre>
  
  <p>Then, I wanted to do some calculations on the data, so I decided to convert the lists into numpy arrays wile performing some calculations:</p>
  
  <pre><code>a = np.asarray([2 * (a + b) for a, b in zip(data_a, data_b])
  b = np.asarray([c / 1000 for c in data_c])
  </code></pre>
  
  <p>Thus, <code>a</code>, <code>b</code>, and <code>c</code> are now defined as <code>&lt;class 'numpy.ndarray'&gt;</code>, with shape <code>(13,)</code>, corresponding to the 13 sheets I imported above. Whenever I want to access the data from the first sheet, I write, for instance, <code>data_a[0]</code>.</p>
  
  <p>However, an error stating that <code>AttributeError: 'Series' object has no attribute 'sqrt'</code> appears if I want to perform something like:</p>
  
  <pre><code>d = np.sqrt(a / b)
  </code></pre>
  
  <p>No error spawns if I manually go write:</p>
  
  <pre><code>d0 = np.sqrt(a[0] / b[0])
  ...
  d12 = np.sqrt(a[12] / b[12])
  </code></pre>
  
  <p>But if I use the <code>type</code> function, <code>d0</code>... <code>d12</code> are now <code>&lt;class 'pandas.core.series.Series'&gt;</code>, whereas <code>a[0]</code> and <code>b[0]</code> are both <code>&lt;class 'numpy.ndarray'&gt;</code>.</p>
  
  <ul>
  <li>What am I doing wrong? </li>
  <li>Why am I not allowed to perform a simple square-root operation?</li>
  </ul>
  
  <p>I wish I could add data, but I am unable to recreate the data format by making synthetic data in Python, which I suspect may be the core of the problem (i.e. I am doing something wrong in terms of the data format).</p>
  
  <p>user32185 requested the output of <code>a[0]</code> and <code>b[0]</code>, respectively: </p>
  
  <pre><code>0     0.883871
  1     0.885714
  2     0.879378
  3     0.865668
  4     0.866014
  5     0.860657
  6     0.866071
  7     0.884389
  8     0.892339
  9     0.892512
  10    0.841590
  11    0.841014
  12    0.882200
  13    0.857546
  14    0.850576
  15    0.853975
  16    0.838710
  dtype: float64
  </code></pre>
  
  <p>and</p>
  
  <pre><code>0     3.701151
  1     3.701938
  2     3.700758
  3     3.690926
  4     3.685027
  5     3.688959
  6     3.712556
  7     3.786099
  8     3.888745
  9     3.956389
  10    3.799078
  11    3.799078
  12    3.778627
  13    3.669295
  14    3.638620
  15    3.606371
  16    3.547379
  Name: b, dtype: float64
  </code></pre>