如何删除熊猫数据框中的唯一行

Question

index                                            SUBJECT
1                                                   test
2                                                  Hello
3                                                  Hello
4                               PRC review - phone calls

AFTER REMOVING

index                                            SUBJECT
2                                                  Hello
3                                                  Hello

I want to delete rows based on only the "SUBJECT" column. How to do this?

Answer 1

Use duplicated

Ex:

import pandas as pd

df = pd.DataFrame({"SUBJECT": ["test", "Hello", "Hello", "PRC review - phone calls"]})
df = df[df.duplicated(subset=["SUBJECT"], keep=False)]
print(df)

Output:

  SUBJECT
1   Hello
2   Hello

Answer 2

You could do:

# get count for each value
s = df.SUBJECT.value_counts()

# get only those that appear more than once
repeated = set(s[s > 1].index.values)

# filter the data-frame base
result = df[df.SUBJECT.isin(repeated)]

print(result)

Output

   index SUBJECT
1      2   Hello
2      3   Hello

Answer 3

检查一下：

df.loc[(df.groupby('SUBJECT').count()>1).sum(axis=1),:]

Answer 4

Solution 1:

using loc..

>>> df.loc[df.duplicated(keep=False), :]
  SUBJECT
1   Hello
2   Hello

Solution 2:

Another way with groupby + transform ..

>>> df[df.groupby('SUBJECT')['SUBJECT'].transform('size') > 1]
  SUBJECT
1   Hello
2   Hello