递归试试?
#!/bin/env python                                                                                   
#encoding=utf-8                                                                                     
# Author: Aaron Shao - shao.dut@gmail.com                                                           
# Last modified: 2015-01-15 12:07                                                                   
# Filename: 
test.py                                                                                 # Description:                                                                                                                                                                                          
a= [['Vodka'], ['Whisky'], ['Scotch'], ['Brandy']]                                                  
b = (['Vodka', 'today', 'nice', 'drink', 'Scotch'], 'Group 2')                                                                                                                                          
def parse(x):                                                                                       
    if isinstance(x, (tuple,list)):                                                                 
        result = set([])                                                                            
        for i in x:                                                                                 
            pass                                                                                    
            result = result | parse(i)                                                              
        return result                                                                               
    elif isinstance(x, str):                                                                        
        return set([x])                                                                             
    else:                                                                                           
        return set([])                                                                                                                                                                                  
x = parse(a)                                                                                        
y = parse(b)                                                                                                                                                                                            
print x & y