import pandas as pd from datetime import datetime ps = pd.Series([datetime(2014, 1, 7), datetime(2014, 3, 13), datetime(2014, 6, 12)]) new = ps.apply(lambda dt: dt.replace(day=1))
import pandas as pd from datetime import datetime ps = pd.Series([datetime(2014, 1, 7), datetime(2014, 3, 13), datetime(2014, 6, 12)]) new = ps.apply(lambda dt: dt.replace(day=1))