#2.去除列表中的重复元素
 #set方法
def removeDuplicates_set(nums):
    l2 = list(set(l1))
    #用l1的顺序排序l2
    #l2.sort(key=l1.index)
    return l2
 #重构字典方法
def removeDuplicates_dict_fromkeys(nums):
    l2 = {}.fromkeys(nums).keys()
    return list(l2)
 #列表推到式，普通方法
def removeDuplicates_normal(nums):
    l2 = []
    [l2.append(i) for i in nums if not i in l2]
    return list(l2)

if __name__==‘__main__‘:
    l1 = [‘b‘,‘c‘,‘d‘,‘b‘,‘c‘,‘a‘,‘a‘]
    print (removeDuplicates_normal(l1))