In Pandas, you can find the first day of the month from a given date by using the to_period method and passing in ‘M’ as the frequency argument.
For example, consider the following date:
import pandas as pd
date = pd.to_datetime("2022-02-15")
You can find the first day of the month for the given date by converting it to a Period object:
first_day_of_month = date.to_period("M").start_time
The resulting first_day_of_month will be the first day of the month of the given date:
Timestamp('2022-02-01 00:00:00')
If you have a column in a DataFrame with dates, you can apply the same logic to all values in the column to find the first day of the month for each date. For example:
import pandas as pd
df = pd.DataFrame({"date": [pd.to_datetime("2022-02-15"),
pd.to_datetime("2021-01-31")]})
df["first_day_of_month"] = df["date"].dt.to_period("M").dt.start_time
The resulting DataFrame will have an additional column first_day_of_month with the first day of the month for each date in the date column:
date first_day_of_month 0 2022-02-15 2022-02-01 1 2021-01-31 2021-01-01