data[data.groupby('tag').pid.transform(len) > 1]
import pandas
import numpy as np
data = pandas.DataFrame(
{'pid' : [1,1,1,2,2,3,3,3],
'tag' : [23,45,62,24,45,34,25,62],
})
bytag = data.groupby('tag').aggregate(np.count_nonzero)
tags = bytag[bytag.pid >= 2].index
print(data[data['tag'].isin(tags)])
产量
pid tag
1 1 45
2 1 62
4 2 45
7 3 62
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