title: Count rows which do not contain some string-Pandas DataFrames
body: <p>I want to count the rows where the dataframe do not contain some string. Eg:</p>
  
  <pre><code>df = pd.DataFrame([[1.1, 1.1, 1.1, 2.6, 2.5, 3.4,2.6,2.6,3.4,3.4,2.6,1.1,1.1,3.3], list('AAABBBBABCBDDD'), ['x/y/z','x/y','x/y/z/n','x/u','x','x/u/v','x/y/z','x','x/u/v/b','-','x/y','x/y/z','x','x/u/v/w']]).T
  df.columns = ['col1','col2','col3']
  
     col1 col2     col3
  0   1.1    A    x/y/z
  1   1.1    A      x/y
  2   1.1    A  x/y/z/n
  3   2.6    B      x/u
  4   2.5    B        x
  5   3.4    B    x/u/v
  6   2.6    B    x/y/z
  7   2.6    A        x
  8   3.4    B  x/u/v/b
  9   3.4    C        -
  10  2.6    B      x/y
  11  1.1    D    x/y/z
  12  1.1    D        x
  13  3.3    D  x/u/v/w
  </code></pre>
  
  <p>In the above dataframe I want to count the rows which do not contain 'u' or 'z'. I know how to use str.contains to get the rows with specific strings.</p>
  
  <pre><code>df.col3.str.contains('u|z')
  </code></pre>
  
  <p>How to get the count of "not" part?</p>