Frequency Table


                    ## Start by defining a simple dictionary
                    x = {'y' : ['A', 'B', 'C', 'A', 'B', 'C'],
                           'z' : ['D', 'E', 'F', 'D', 'E', 'F']}  
                    
                    import pandas as pd
                    x = pd.DataFrame(x)              # format x as DataFrame
                    
                    y_freq = x['y'].value_counts()  # pass column 'y' of DataFrame x to value_counts
                    print(y_freq)