Pandas: how to merge two dataframes on offset dates?

Question

I\'d like to merge two dataframes, df1 & df2, based on whether rows of df2 fall within a 3-6 month date range after rows of df1. For example:

df1 (for each company I

Answer 1

This is actually one of those rare questions where the algorithmic complexity might be significantly different for different solutions. You might want to consider this over the niftiness of 1-liner snippets.

Algorithmically:

• sort the larger of the dataframes according to the date

• for each date in the smaller dataframe, use the bisect module to find the relevant rows in the larger dataframe

For dataframes with lengths m and n, respectively (m < n) the complexity should be O(m log(n)).