列表的元素进行统计数量

s = [1,1,4,3,4,4,2]

1、使用pandas中的value_counts方法

dd = pd.value_counts(s)

 2、使用for循环以及np.unique

1.  
   s = [1,1,4,3,4,4,2]
2.  
   s1 = np.unique(s)
3.  
   num = []
4.  
   for i in s1:
5.  
   num.append(s.count(i))

3、与2类似，使用字典

1.  
   s = [1,1,4,3,4,4,2]
2.  
   s1 = np.unique(s)
3.  
   dicts = {}
4.  
   for i in s1:
5.  
   dicts[i] = s.count(i)

4、使用collections中的Counter

1.  
   from collections import Counter
2.  
    
3.  
   s = [1,1,4,3,4,4,2]
4.  
   num = Counter(s)
5.  
   for i,j in num.items():
6.  
   print(i,j)

5、使用groupby函数

1.  
   import pandas as pd
2.  
   s = [1,1,4,3,4,4,2]
3.  
   f = pd.Series(s).groupby(s).size() #size可查看多少
4.  
   dicts1 = {}
5.  
   for i,j in zip(f.index,f.values):
6.  
   dicts1[i] = j

这个也可以用于dataframe中

1.  
   dicts = {}
2.  
   df = pd.read_excel('选修课.xlsx')
3.  
   dd = df.groupby(df['上课班级']).size()
4.  
   for i,j in zip(dd.index,dd.values):
5.  
   dicts[i] = j
6.  
   print(i,j)

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