title: Comparing dataframe column with single value in pandas python
body: <p>I built a data frame on python using an inputed SQL query. Afer this I name my columns and make sure it's nice to isolate columns with NaN values :</p>
  
  <pre><code>cursor.execute(raw_input("Enter your SQL query: "))
  records = cursor.fetchall()
  import pandas as pd
  dframesql = pd.DataFrame(records)
  dframesql.columns = [i[0] for i in cursor.description]
  </code></pre>
  
  <p>The problem comes after when I want to compare the number of rows with data with the total number of rows in the data frame :</p>
  
  <pre><code>dframelines = len(dframesql)
  dframedesc = pd.DataFrame(dframesql.count())
  </code></pre>
  
  <p>When I try to compare dframedesc with dframelines, I get an error</p>
  
  <pre><code>nancol = []
  for line in dframedesc:
      if dframedesc &lt; dframelines:
          nancol.append(line)
  
  ValueError: The truth value of a DataFrame is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().
  </code></pre>
  
  <p>Thanks in advance !</p>