Merging two Pandas Dataframes using Regular Expressions - regex

Question

I'm new to Python and Pandas but I try to use Pandas Dataframes to merge two dataframes based on regular expression.
I have one dataframe with some 2 million rows. This table contains data about cars but the model name is often specified in - lets say - a creative way, e.g. 'Audi A100', 'Audi 100', 'Audit 100 Quadro', or just 'A 100'. And the same for other brands. This is stored in a column called "Model". In a second model I have the manufacturer.
Index
Model
Manufacturer
0
A 100
Audi
1
A100 Quadro
Audi
2
Audi A 100
Audi
...
...
...
To clean up the data I created about 1000 regular expressions to search for some key words and stored it in a dataframe called 'regex'. In a second column of this table I save the manufacture. This value is used in a second step to validate the result.
Index
RegEx
Manufacturer
0
.* A100 .*
Audi
1
.* A 100 .*
Audi
2
.* C240 .*
Mercedes
3
.* ID3 .*
Volkswagen
I hope you get the idea.
As far as I understood, the Pandas function "merge()" does not work with regular expressions. Therefore I use a loop to process the list of regular expressions, then use the "match" function to locate matching rows in the car DataFrame and assign the successfully used RegEx and the suggested manufacturer.
I added two additional columns to the cars table 'RegEx' and 'Manufacturer'.
for index, row in regex.iterrows():
cars.loc[cars['Model'].str.match(row['RegEx']),'RegEx'] = row['RegEx']
cars.loc[cars['Model'].str.match(row['RegEx']),'Manufacturer'] = row['Manfacturer']
I learnd 'iterrows' should not be used for performance reasons. It takes 8 minutes to finish the loop, what isn't too bad. However, is there a better way to get it done?
Kind regards
Jiriki

Answer 1

I have no idea if it would be faster (I'll be glad, if you would test it), but it doesn't use iterrows():
regex.groupby(["RegEx", "Manufacturer"])["RegEx"]\
.apply(lambda x: cars.loc[cars['Model'].str.match(x.iloc[0])])
EDIT: Code for reproduction:
cars = pd.DataFrame({"Model": ["A 100", "A100 Quatro", "Audi A 100", "Passat V", "Passat Gruz"],
"Manufacturer": ["Audi", "Audi", "Audi", "VW", "VW"]})
regex = pd.DataFrame({"RegEx": [".*A100.*", ".*A 100.*", ".*Passat.*"],
"Manufacturer": ["Audi", "Audi", "VW"]})
#Output:
# Model Manufacturer
#RegEx Manufacturer
#.*A 100.* Audi 0 A 100 Audi
# 2 Audi A 100 Audi
#.*A100.* Audi 1 A100 Quatro Audi
#.*Passat.* VW 3 Passat V VW
# 4 Passat Gruz VW