（Note）Python 统计列表中各元素出现的次数

演示列表：

Demo_list=[1,2,3,3,3,5,6,2,2,0,4,5,2,7,8,4,5,1,3,9,8,7]

1.统计列表中不同元素的个数

Demo_list=[1,2,3,3,3,5,6,2,2,0,4,5,2,7,8,4,5,1,3,9,8,7] 

List_to_set=set(Demo_list)

print(List_to_set)
print(len(List_to_set))

Result：

{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
10

2.统计列表中各元素出现的次数（方法1）

Demo_list=[1,2,3,3,3,5,6,2,2,0,4,5,2,7,8,4,5,1,3,9,8,7] 


Demo_dict={}
for item in List_to_set:
    Demo_dict.update({item:Demo_list.count(item)})
    
print(Demo_dict)

Result：

{0: 1, 1: 2, 2: 4, 3: 4, 4: 2, 5: 3, 6: 1, 7: 2, 8: 2, 9: 1}

3.统计列表中各元素出现的次数（方法2）

Demo_list=[1,2,3,3,3,5,6,2,2,0,4,5,2,7,8,4,5,1,3,9,8,7] 


Demo_dict={}
for key in Demo_list:
    Demo_dict[key]=Demo_dict.get(key,0)+1
    
print(Demo_dict)

Result：

{1: 2, 2: 4, 3: 4, 5: 3, 6: 1, 0: 1, 4: 2, 7: 2, 8: 2, 9: 1}

4.统计列表中各元素出现的次数（方法3）

Demo_list=[1,2,3,3,3,5,6,2,2,0,4,5,2,7,8,4,5,1,3,9,8,7] 


# 利用Pandas模块下的value_counts函数
import pandas as pd
Demo_result=pd.value_counts(Demo_list)

print(Demo_result)

Result：

2    4
3    4
5    3
1    2
4    2
7    2
8    2
6    1
0    1
9    1
dtype: int64

5.统计列表中各元素出现的次数（方法4）

Demo_list=[1,2,3,3,3,5,6,2,2,0,4,5,2,7,8,4,5,1,3,9,8,7] 


# 利用collections模块下的Counter函数
from collections import Counter
Demo_result=Counter(Demo_list)
Demo_result=dict(Demo_result)

print(Demo_result)

Result：

{1: 2, 2: 4, 3: 4, 5: 3, 6: 1, 0: 1, 4: 2, 7: 2, 8: 2, 9: 1}

Python Code：

# Python Count


import warnings
warnings.filterwarnings('ignore')


Demo_list=[1,2,3,3,3,5,6,2,2,0,4,5,2,7,8,4,5,1,3,9,8,7] 


# 0.统计列表中不同元素的个数
List_to_set=set(Demo_list)

print(List_to_set)
print(len(List_to_set))


# 1.统计列表中各元素出现的次数 (Type:0)
Demo_dict={}
for item in List_to_set:
    Demo_dict.update({item:Demo_list.count(item)})
    
print(Demo_dict)


# 2.统计列表中各元素出现的次数 (Type:1)
Demo_dict={}
for key in Demo_list:
    Demo_dict[key]=Demo_dict.get(key,0)+1
    
print(Demo_dict)


# 3.统计列表中各元素出现的次数 (Type:2)
# 利用Pandas模块下的value_counts函数
import pandas as pd
Demo_result=pd.value_counts(Demo_list)

print(Demo_result)


# 4.统计列表中各元素出现的次数 (Type:3)
# 利用collections模块下的Counter函数
from collections import Counter
Demo_result=Counter(Demo_list)
Demo_result=dict(Demo_result)

print(Demo_result)

Result：