Python 3.x Python3，带有pandas.dataframe，如何通过一些规则选择某些数据来显示

我有一个pandas.dataframe，我想根据一些规则选择某些数据

以下代码生成数据帧

import datetime
import pandas as pd
import numpy as np

today = datetime.date.today()
dates = list()
for k in range(10):
    a_day = today - datetime.timedelta(days=k)
    dates.append(np.datetime64(a_day))

np.random.seed(5)
df = pd.DataFrame(np.random.randint(100, size=(10, 3)),
                  columns=('other1', 'actual', 'other2'),
                  index=['{}'.format(i) for i in range(10)])

df.insert(0, 'dates', dates)
df['err_m'] = np.random.rand(10, 1)*0.1
df['std'] = np.random.rand(10, 1)*0.05
df['gain'] = np.random.rand(10, 1)

现在，我想按照以下规则进行选择：

1. compute the sum of 'err_m' and 'std', then sort the df so that the sum is descending
2. from the result of step 1, select the part where 'actual' is > 50    

谢谢

创建一个新列，然后按此列排序：

df['errsum'] = df['err_m'] + df['std']
# Return a sorted dataframe
df_sorted = df.sort('errsum', ascending = False) 

选择所需的行

 # Create an array with True where the condition is met
 selector = df_sorted['errsum'] > 50
 # Return a view of sorted_dataframe with only the lines you want
 df_sorted[selector]