How floor a date to the first date of that month?

Question

I have a pandas DataFrame with index column = date.

Input:

            value
date    
1986-01-31  22.93
1986-02-28  15.46

Answer 1

there is a pandas issue about the floor problem

the suggested way is

import pandas as pd
pd.to_datetime(df.date).dt.to_period('M').dt.to_timestamp()