title: get a column count without "NaN"
body: <p>How do I count the number of columns without <code>NaN</code> ?</p>
  
  <pre><code>import pandas as pd
  df = pd.DataFrame(columns = ['name', 'age', 'favorite_color', 'grade','NaN'])
  print(len(df.columns))
  </code></pre>
  
  <p><strong>Output:</strong> 5</p>
  
  <p>But looking Output: 4</p>