python - Case insensitive pandas dataframe.merge

Question

I am struggling with the easiest way to do a case insensitive merge in pandas. Is there a way to do it right on the merge? Do I need to use (?i) or a regex with ignorecase? In my code snippet below I am joining some Countries where it may be "United States" in one file and "UNITED STATES" in another and I just want to take the case out of the equation. Thank you!

import pandas as pd
import csv
import sys

env_path = sys.argv[1]
map_path = sys.argv[2]


df_address = pd.read_csv(env_path + "\address.csv")
df_CountryMapping = pd.read_csv(map_path + "CountryMapping.csv")

df_merged = df_address.merge(df_CountryMapping, left_on="Country", right_on="NAME", how="left")

....

Answer 1

Lowercase the values in the two columns that will be used to merge, and then merge on the lowercased columns

df_address['country_lower'] = df_address['Country'].str.lower()
df_CountryMapping['name_lower'] = df_CountryMapping['NAME'].str.lower()
df_merged = df_address.merge(df_CountryMapping, left_on="country_lower", right_on="name_lower", how="left")