python 统计数组中元素出现次数并进行排序

lis = [12,34,456,12,34,66,223,12,5,66,12,23,66,12,66,5,456,12,66,34,5,34]def test1():    #进行去重    c = []    for i in lis:        if i not in c:            c.append(i)    #进行统计，生成二维列表    b = []    for i in c:        num = 0        for j in range(len(lis)):            if lis[j] == i:                num += 1        a = []        a.append(i)        a.append(num)        b.append(a)    # 排序算法，按出现次数进行降序排列    for i in range(len(b)):        for j in range(i,len(b)):            if b[i][1] < b[j][1]:                temp = b[i]                b[i] = b[j]                b[j] = temp    print(b)def test2():    # set进行去重，进行统计生成二维列表    b = []    for i in list(set(lis)):        num = 0        for j in range(len(lis)):            if lis[j] == i:                num += 1        a = []        a.append(i)        a.append(num)        b.append(a)    # 排序算法，按出现次数进行降序排列    for i in range(len(b)):        for j in range(i,len(b)):            if b[i][1] < b[j][1]:                temp = b[i]                b[i] = b[j]                b[j] = temp    print(b)def test3():    # 统计元素出现次数，元素为key，次数为value，生成字典    a = {}    for i in lis:        if i in a:            a[i] = a[i] + 1        else:            a[i] = 1    # 使用sorted对字典进行排序    b = sorted(a.items(),key=lambda item:item[1],reverse=True)    print(b)def test4():    from  collections import Counter    import operator    #进行统计    a = dict(Counter(lis))    #进行排序    b= sorted(a.items(), key=operator.itemgetter(1),reverse=True)    print(b)if __name__ == '__main__':    test1()    test2()    test3()    test4()

输出结果如下：

[[12, 6], [66, 5], [34, 4], [5, 3], [456, 2], [223, 1], [23, 1]][[12, 6], [66, 5], [34, 4], [5, 3], [456, 2], [23, 1], [223, 1]][(12, 6), (66, 5), (34, 4), (5, 3), (456, 2), (23, 1), (223, 1)][(12, 6), (66, 5), (34, 4), (5, 3), (456, 2), (23, 1), (223, 1)]

这是面试过程中遇到的一个问题找到的解决方法，总结了一下，小编是初学者，还需不断努力学习。