从 dataframe 中删除值在整列中仅出现一次的行

Question

I have a data frame like this:

import pandas as pd

data = [['bob', 1], ['james', 4], ['joe', 4], ['joe', 1], ['bob', 3], ['wendy', 5], ['joe', 7]]
df = pd.DataFrame(data, columns=['name', 'score'])
print(df)

Looking like:

    name  score
0    bob      1
1  james      4
2    joe      4
3    joe      1
4    bob      3
5  wendy      5
6    joe      7

I would like to drop all persons with only a single occurrence in a Pythonic way ie the result should look like:

    name  score
0    bob      1
2    joe      4
3    joe      1
4    bob      3
6    joe      7

... and how would I do the same with entries that only have 1 or 2 occurrences? ie

    name  score
2    joe      4
3    joe      1
6    joe      7

Answer 1

try this, DataFrameGroupBy.nunique to get count of unique elements in each group & apply isin to filter occurrences.

g = df.groupby(['name'])['score'].transform('nunique')

---

df[~g.isin([1])]

  name  score
0  bob      1
2  joe      4
3  joe      1
4  bob      3
6  joe      7

---

df[~g.isin([1,2])]

  name  score
2  joe      4
3  joe      1
6  joe      7