Python统计列表中每个元素出现次数的4种实现

from collections import Counter
arr=[1,2,5,1,1,5,6,3,3,2,2,4,8]
# arr=Counter(lists)
# print(arr)
def counter(arr):
    return Counter(arr)
print(counter(arr))  

"""
方法二：使用for循环
"""
result=['python','java','python','flask','django','flask']
result_dic={}
for item_str in result:
    if item_str not in result_dic:
        result_dic[item_str]=1
    else:
        result_dic[item_str]+=1
print(result_dic)

"""
方法三：利用list中的函数count,获取每个元素的出现次数
"""
list1=[1,5,5,2,2,2,1,3]
def all_list(list1):
    result = {}
    for i in set(list1):
        result[i]=list1.count(i)
    return result
print(all_list(list1))

"""
方法四：利用Numpy索引，获取每个元素的出现次数
"""
import numpy as np
list2=[5,5,5,8,8,9,1]
def num(lis):
    lis=np.array(lis)
    key=np.unique(lis)
    result={}
    for k in key:
        mask =(lis == k)
        list_new=lis[mask]
        v=list_new.size
        result[k]=v
    return result
print(num(list2))