python 统计数组中元素出现次数并进行排序的实例

如下所示：

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)]

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