title: How to calculate conditional probability of values in dataframe pandas-python?
body: <p>I want to calculate conditional probabilites of ratings('A','B','C') in ratings column. </p>
  
  <pre><code>    company     model    rating   type
  0   ford       mustang     A      coupe
  1   chevy      camaro      B      coupe
  2   ford       fiesta      C      sedan
  3   ford       focus       A      sedan
  4   ford       taurus      B      sedan
  5   toyota     camry       B      sedan
  </code></pre>
  
  <p>Output:</p>
  
  <pre><code>Prob(rating=A) = 0.333333 
  Prob(rating=B) = 0.500000 
  Prob(rating=C) = 0.166667 
  
  Prob(type=coupe|rating=A) = 0.500000 
  Prob(type=sedan|rating=A) = 0.500000 
  Prob(type=coupe|rating=B) = 0.333333 
  Prob(type=sedan|rating=B) = 0.666667 
  Prob(type=coupe|rating=C) = 0.000000 
  Prob(type=sedan|rating=C) = 1.000000 
  </code></pre>
  
  <p>Any help, Thanks..!!</p>