考虑 pandas 中的以下数据框
date action price
20150101 buy 10
20150102 buy 9
20150103 sell 11
20150104 sell 10
20150105 buy 8
20150106 sell 9
如果我想在“出售”变为“购买”时添加行,并且插入的行只是前一行的副本,除了将“出售”更改为“购买”之外,如下所示:
date action price
20150101 buy 10
20150102 buy 9
20150103 sell 11
20150104 sell 10
**20150104 buy 10**
20150105 buy 8
20150106 sell 9
**20150106 buy 9 **
感谢您的帮助。
最佳答案
您可以使用
来识别过渡行mask = (df['action'] == 'sell') & (df['action'].shift(-1) != 'sell')
# In [229]: mask
# Out[229]:
# 0 False
# 1 False
# 2 False
# 3 True
# 4 False
# 5 True
# Name: action, dtype: bool
然后您可以创建一个新的 DataFrame,其中包含 mask
为 True 的行:
new = df.loc[mask].copy()
将操作设置为“购买”
:
new['action'] = 'buy'
# date action price
# 3 20150104 buy 10
# 5 20150106 buy 9
构建一个新的 DataFrame,连接 df
和 new
:
df = pd.concat([df, new])
并按日期
排序:
df = df.sort(['date'])
例如,
import pandas as pd
df = pd.read_table('data', sep='\s+')
mask = (df['action'] == 'sell') & (df['action'].shift(-1) != 'sell')
new = df.loc[mask].copy()
new['action'] = 'buy'
df = pd.concat([df, new])
df = df.sort(['date'])
df = df.reset_index(drop=True)
print(df)
产量
date action price
0 20150101 buy 10
1 20150102 buy 9
2 20150103 sell 11
3 20150104 sell 10
4 20150104 buy 10
5 20150105 buy 8
6 20150106 sell 9
7 20150106 buy 9
关于python - 根据 pandas 数据框中的列值插入行,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/30145357/