Python: Difference in dates (column of dates vs. variable date)

Question

I have a column of various dates and wanted to add another column to the dataframe that shows the difference between the dates in the column versus a date in various that I have set.

enddate = date(2021, 10, 15)

Would something like:

I tried below but did returns error:

from dateutil.relativedelta import relativedelta
metric_df['term'] = relativedelta(metric_df['maturity'], enddate).years

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

Answer 1

relativedelta doesn't give you fractional years afaik, but you can easily calculate them yourself:

import pandas as pd

# dummy data
metric_df = pd.DataFrame({'maturity': ["9/22/2025", "11/10/2033", "3/1/2023"]})

# convert to datetime, so we can run calculations with date & time
metric_df['maturity'] = pd.to_datetime(metric_df['maturity'])

# to get fractional years, we calculate difference in days and divide
# by the average number of days per year:
metric_df['term'] = (metric_df['maturity'] - 
                         pd.Timestamp("2021-10-15")).dt.days / 365.25

metric_df['term']
0     3.937029
1    12.071184
2     1.374401
Name: term, dtype: float64