如何按列名过滤值，然后将具有相同值的行提取到另一个CSV文件？ Python /熊猫

Question

I have a pandas DataFrame with 4 columns, the first being "ID NUMBER". I am trying to filter "ID NUMBER" and get the same values bundled together. After that I want to extract each one that have the same values to a different csv file with their respected name.

DataFrame:

     ID Number    col2           col3     DATE
0   111            0.5          -0.6    20160104
1   118           -0.1          -0.6    20160104
2   11D            0.3          -1.1    20160104
3   111           -0.7          -0.9    20150102


 ***Output I need:***
 Number ID    col2           col3     DATE
0   111            0.5          -0.6    20160104
1   111           -0.7          -0.9    20150102

I have attempted to do something, however I could not find anything about how to filter a columns, and then extract online. Thank you!

Answer 1

You can use duplicated with param keep=False so it returns True for all duplicated rows and mask the df:

In [16]:
df[df['ID Number'].duplicated(keep=False)]

Out[16]:
  ID Number  col2  col3      DATE
0       111   0.5  -0.6  20160104
3       111  -0.7  -0.9  20150102

For the second part you can do:

gp = df[df['ID Number'].duplicated(keep=False)].groupby('ID Number')
gp.apply(lambda x: x.to_csv(str(x.name) + '.csv')

EDIT

Actually if you're just wanting to write all rows with the same ID number to a named csv then:

df.groupby('ID Number').apply(lambda x: x.to_csv(str(x.name) + '.csv'))

Should do what you want