dataframe分类排序优化问题

Question

我想取dataframe 'category'列两个字母中，另外一列'data'的最大4个，并按照一定的规则排序，代码如下，请问有什么更简单的方法么？

import numpy as np
from time import time
import pandas as pd

df = pd.DataFrame()
n = 200
df['category'] = np.random.choice(('A', 'B'), n)
df['data'] = np.random.randint(1, 10000, len(df))
a = df[df['category'] == 'A'].sort_values(by='data', ascending=False).head(4)
b = df[df['category'] == 'B'].sort_values(by='data', ascending=False).head(4)
df = pd.concat([a, b]).sort_values(by=['category','data'],ascending=[True,False]).reset_index(drop=True)
print(df)

结果如下

  category  data
0        A  9889
1        A  9879
2        A  9873
3        A  9822
4        B  9909
5        B  9855
6        B  9775
7        B  9689

Answer 1

试试这个

temp  = df.groupby('category')['data'].nlargest(4).reset_index()
temp.drop('level_1',axis=1)