title: Get single value from dataframe pandas
body: <p>I have a dataframe A:</p>
  
  <pre><code>       's'   'S'   'T'
   0     'abc'  'a'   12
   1     'def'  'b'   15
   2     'abc'  'b'   1.4
  </code></pre>
  
  <p>Now I want to have the value of 'T' where 's' == 'abc' and 'S' == 'b'</p>
  
  <p>So I tried:</p>
  
  <pre><code>  idx = (A['s'] == 'abc') &amp; (A['S'] == 'b')
  </code></pre>
  
  <p>but I see .get_value() is depricated and:</p>
  
  <pre><code> number = A.at[idx,'T']
  </code></pre>
  
  <p>gives this error:</p>
  
  <pre><code>ValueError: At based indexing on an integer index can only have integer indexers
  </code></pre>
  
  <p>EDIT:</p>
  
  <pre><code> number = A.loc[idx, 'T']
  </code></pre>
  
  <p>returns a dataframe and not the value (integer or float)</p>
  
  <pre><code> print(number)
  
   2    1.4
   Name: T, dtype: float64
  </code></pre>
  
  <p>When doing this:</p>
  
  <pre><code> number2 = 1.3
   if (number != number2):
  </code></pre>
  
  <p>I get:</p>
  
  <pre><code>  ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all(). 
  </code></pre>