Python基础-List找重复数

请从L=[1,10,20,50,20,20,1]中找出重复数。

 L=[1,10,20,50,20,20,1]
 L1=[]
 for i in L:
     if(L.count(i)>1):
         L1.append(i)
 L2=[]
 for i in L1:
     if i not in L2:
         L2.append(i)
 print L2