[Python] How to extract a substring from a column in a dataframe based in the column from...

I have found a solution from my problem, but it is clearly the most dumb and inefficient one. I was hoping that someone could help me with a proper solution.

I have two data frames containing a column with a telephone number. df1["telephone"] can have one or more numbers separated by commas and df2["telephone"] has only single numbers:

df1["telephone"]

telephone

115879878
411564656
465464654,45646546
464665465,46456465,87972315
123165648


df2["telephone"]

telephone

156465456
132131321
879878999
456489798
546489798
465478978


What I want to do is, check if one of the numbers in df1["telephone"] is in df2["telefone"] and create a column with the matched number.

I have managed to do this using the following code:

df1['telephone'] = df1['telephone'].astype(str)
df2["telephone"] = df2["telephone"].astype(str)

telephone_match = []

for telephone_1 in df1['telephone']:
telephone_found = False

for telephone_2 in df2["telephone"]:

if (telephone_2 in telephone_1):
telephone_match.append(telephone_2)
telephone_found = True
continue

if (not telephone_found):
telephone_match.append(False)

df1['matches'] = telephone_match


This works, but it takes ages to run. I pretty sure it is the dumbest possible method, but I have no idea how to do this efficiently. Can someone please help me?

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