所有
我有两个数据帧：allHoldings和Longswap
allHoldings
prime_broker_id country_name position_type
0 CS UNITED STATES LONG
1 ML UNITED STATES LONG
2 CS AUSTRIA SHORT
3 HSBC FRANCE LONG
4 CITI UNITED STATES SHORT
11 DB UNITED STATES SHORT
12 JPM UNITED STATES SHORT
13 CS ITALY SHORT
14 CITI TAIWAN SHORT
15 CITI UNITED KINGDOM LONG
16 DB FRANCE LONG
17 ML SOUTH KOREA LONG
18 CS AUSTRIA SHORT
19 CS JAPAN LONG
26 HSBC FRANCE SHORT
和Longswap
prime_broker_id country_name longSpread
0 ML AUSTRALIA 30.0
1 ML AUSTRIA 30.0
2 ML BELGIUM 30.0
3 ML BRAZIL 50.0
4 ML CANADA 20.0
5 ML CHILE 50.0
6 ML CHINA - A 75.0
7 ML CZECH REPUBLIC 45.0
8 ML DENMARK 30.0
9 ML EGYPT 45.0
10 ML FINLAND 30.0
11 ML FRANCE 30.0
12 ML GERMANY 30.0
13 ML HONG KONG 30.0
14 ML HUNGARY 45.0
15 ML INDIA 75.0
16 ML INDONESIA 75.0
17 ML IRELAND 30.0
18 ML ISRAEL 45.0
19 ML ITALY 30.0
20 ML JAPAN 30.0
21 ML SOUTH KOREA 50.0
22 ML LUXEMBOURG 30.0
23 ML MALAYSIA 75.0
24 ML MEXICO 50.0
25 ML NETHERLANDS 30.0
26 ML NEW ZEALAND 30.0
27 ML NORWAY 30.0
28 ML PHILIPPINES 75.0
我之前已经加入了很多数据帧，但我仍然感到困惑的是为什么它不能用于这个例子。
这是我的代码：
allHoldings=pd.merge(allHoldings, Longswap, how='left', left_on = ['prime_broker_id','country_name'], right_on=['prime_broker_id','country_name'])
我的结果是
prime_broker_id country_name position_type longSpread
0 CS UNITED STATES LONG NaN
1 ML UNITED STATES LONG NaN
2 CS AUSTRIA SHORT NaN
3 HSBC FRANCE LONG NaN
4 CITI UNITED STATES SHORT NaN
5 DB UNITED STATES SHORT NaN
6 JPM UNITED STATES SHORT NaN
7 CS ITALY SHORT NaN
你可以看到longSpread列是一个没有任何意义的NaN。从longSwap数据框中，应该填充此列。
我不确定为什么左连接不能在这里工作。
感谢任何帮助。
答案 0 :(得分：0)
这是删除空格并使左连接成功的答案
allHoldings.prime_broker_id.str.strip()
array(['CS', 'ML', 'HSBC', 'CITI', 'DB', 'JPM', 'WFPBS'], dtype=object)