以前面试的时候遇到过这个问题，今天闲着整理了以下，大概想到以下三种方法。

<span style="font-size:18px;">class delect_duplicate:
    def method_set(self,mlist):
        print("method_set is called")
        print("before process mlist is", mlist)
        l2 = set(mlist)
        print("after processed by method_xunhuan, the mlist is",l2)
    def method_xunhuan(self,mlist):
        print("method_xunhuan is called")
        print("before process mlist is", mlist)
        if mlist:
            mlist.sort()
            last = mlist[-1]
            for i in range(len(mlist) - 2, -1, -1):
                if last == mlist[i]:
                    del mlist[i]
                else:
                    last = mlist[i]
        print("after processed by method_xunhuan, the mlist is",mlist)
    def method3(self,mlist):
        print("method3 is called")
        print("before process mlist is", mlist)
        temp = []
        [temp.append(i) for i in mlist if not i in temp]
        print("after processed by method3, the result is",temp)</span>

第二种方法是对列表的元素排序后从后往前比较，去除相同元素，但是前两种方法都有一个缺点，就是处理后元素的位置改变了，

第三种方法是用两个列表进行处理，不改变元素的位置，测试代码如下：

<span style="font-size:18px;">if __name__ == '__main__':
    A = [1, 5, 4, 8, 9, 2, 4, 5, 1]
    B = [1, 5, 4, 8, 9, 2, 4, 5, 1]
    C = [1, 5, 4, 8, 9, 2, 4, 5, 1]
    s = delect_duplicate()
    s.method_set(A)
    s.method_xunhuan(B)
    s.method3(C)</span>

运行结果如下：

<span style="font-size:18px;">method_set is called
before process mlist is [1, 5, 4, 8, 9, 2, 4, 5, 1]
after processed by method_xunhuan, the mlist is {1, 2, 4, 5, 8, 9}
method_xunhuan is called
before process mlist is [1, 5, 4, 8, 9, 2, 4, 5, 1]
after processed by method_xunhuan, the mlist is [1, 2, 4, 5, 8, 9]
method3 is called
before process mlist is [1, 5, 4, 8, 9, 2, 4, 5, 1]
after processed by method3, the result is [1, 5, 4, 8, 9, 2]</span>

Python 列表元素去重的3种方法