pandas find which half year a date belongs to

I have the following pandas data frame with a date column. How can I add a column specifying which half year the date belongs to?

Convert dates to datetimes and then use numpy.where with compare for less or equal:

df['date'] = pd.to_datetime(df['date'], dayfirst=True)

df['half year'] = np.where(df['date'].dt.month.le(6), 'H1', 'H2')
print (df)
        date half year
0 1993-09-09        H2
1 1993-09-11        H2
2 1994-01-23        H1
3 1993-03-18        H1

Solution without numpy with change mask for greater like 6, add 1 and convert to strings:

df['date'] = pd.to_datetime(df['date'], dayfirst=True)

df['half year'] = 'H' + df['date'].dt.month.gt(6).add(1).astype(str)
print (df)
        date half year
0 1993-09-09        H2
1 1993-09-11        H2
2 1994-01-23        H1
3 1993-03-18        H1

Try:

df['half year'] = 'H' + pd.to_datetime(df['date']).dt.month.floordiv(6).add(1).astype(str)
print(df)

# Output
         date half year
0  09-09-1993        H2
1  18-03-1993        H1