根据另一列的重复项删除一列的重复项，将另一列重复项保留在 pandas

Question

Keeping the duplicates of name column, I want to drop the duplicates of Count column except the unique values of name column

here is a example df

Count	name
yes	jhon
yes	marry
yes	marry
yes	ishita
yes	ishita
yes	ishita

The result I want as:

Count	name
yes	jhon
yes	marry
	marry
yes	ishita
	ishita
	ishita

#pandas #python

Answer 1

The logic is

• groupby() and cumcount() instances of Name
• 0th instance, keep Count otherwise set to NaN

df = pd.read_csv(io.StringIO("""Count   name
yes jhon
yes marry
yes marry
yes ishita
yes ishita
yes ishita"""),sep="\t")

df.Count=np.where(df.groupby("name",as_index=False)["name"].cumcount()==0, df.Count, np.nan)

	Count	name
0	yes	jhon
1	yes	marry
2	nan	marry
3	yes	ishita
4	nan	ishita
5	nan	ishita