We have the following Pandas Dataframe:

# Stackoverflow question
data = {'category':[1, 2, 3, 1, 2, 3, 1, 2, 3], 'date':['2000-01-01', '2000-01-01', '2000-01-01', '2000-01-02', '2000-01-02', '2000-01-02', '2000-01-03', '2000-01-03', '2000-01-03']}  
df = pd.DataFrame(data=data)
df['date'] = pd.to_datetime(df['date'])
df

category    date
0   1   2000-01-01
1   2   2000-01-01
2   3   2000-01-01
3   1   2000-01-02
4   2   2000-01-02
5   3   2000-01-02
6   1   2000-01-03
7   2   2000-01-03
8   3   2000-01-03

How can we query this dataframe to find the date 2000-01-02 with category 3? So we are looking for the row with index 5.

It should be accomplished without set_index(‘date’).
The reason for this is as follows, when setting the index on the actual data rather than the example data I receive the following error:

InvalidIndexError: Reindexing only valid with uniquely valued Index objects

>Solution :

Take a subset of relevant category, subtract the target date, and get idxmin

tmp = df.loc[df.category.eq(3)]
(tmp.date - pd.to_datetime("2000-01-02")).abs().idxmin()
# 5