title: Pandas: select cell value using pd.at with condition
body: <p>I'd like to select specific cell values from a Pandas Dataframe. I want to filter out rows with specific values in column A, and then get the values from column B. </p>
  
  <p>From what I understand, the correct way to do this is to use <code>df.at</code>, so I've tried</p>
  
  <pre><code>df.at(df['Column A' == column_A_value]['Column B'])
  </code></pre>
  
  <p>but this doesn't work. I've also tried, as a hack, </p>
  
  <pre><code>str(['Column A' == column_A_value]['Column B'])
  </code></pre>
  
  <p>doesn't work either. </p>
  
  <p>What is the right way to do this?</p>
  
  <p>Edit: </p>
  
  <p>What I'm trying to do is to output the values inside of a bigger loop, something like:</p>
  
  <pre><code>while condition:
      for val in some_column_A_values:
          print("{},{}".format('stuff', df.at(df['Column A' == val]['Column B'])), file=myfile)
  </code></pre>