Python 多維數組求下標

def list_index(List,sub_ele,Index=[],a=0):    
    for i in List: 
        print 'search...'+`Index`
        if  isinstance(i,list):                 
            Index.append(a)            
            x=list_index(i,sub_ele,Index,a=0)            
            if x:
               return x
            Index.pop()
        elif sub_ele == i:            
            Index.append(a)
            print 'success:'+`Index`
            return Index            
        a+=1

List=['a','i',['b','c'],'e',['f',['g',['z'],['y',['k']],['j',['n',['m'],'w'],'x']],'h'],'l']
sub_ele='y'
print list_index(List,sub_ele)