How to merge two data frames based on nearest date

Question

I want to merge two data frames based on two columns: \"Code\" and \"Date\". It is straightforward to merge data frames based on \"Code\", however in case of \"Date\" it bec

Answer 1

Here's an alternative solution:

1. Merge on Code.

2. Add a date difference column according to your need (I used abs in the example below) and sort the data using the new column.

3. Group by the records of the first data frame and for each group take a record from the second data frame with the closest date.

Code:

df = df1.reset_index()[column_names1].merge(df2[column_names2], on='Code')
df['DateDiff'] = (df['Date1'] - df['Date2']).abs()
df.sort_values('DateDiff').groupby('index').first().reset_index()