在保留 pandas 的NaN的同时放下重复项
问题描述：
使用drop_duplicates()方法时，我减少了重复项，但也将所有NaNs合并为一个条目.
When using the drop_duplicates() method I reduce duplicates but also merge all NaNs into one entry. How can I drop duplicates while preserving rows with an empty entry (like np.nan, None or '')?
import pandas as pd
df = pd.DataFrame({'col':['one','two',np.nan,np.nan,np.nan,'two','two']})
Out[]:
col
0 one
1 two
2 NaN
3 NaN
4 NaN
5 two
6 two
df.drop_duplicates(['col'])
Out[]:
col
0 one
1 two
2 NaN
答
尝试
df[(~df.duplicated()) | (df['col'].isnull())]
结果是:
col
0 one
1 two
2 NaN
3 NaN
4 NaN