Python: Map a string value from one dataframe to another dataframe using a id, while creating a new column in the older dataframe

Question

i turned a json file into a dataframe, but I am unsure of how to map a certain value from the json dataframe onto the existing data frame i have.

df1 =     # (2nd column does'nt matter just there)

category_id	tags
1	a
1	a
10	b
10	c
40	d

df2(json) =

id	title
1	film
2	music
3	travel
4	cooking
5	dance

I would like to make a new column in df1, that maps the titles from the df2 onto df1 corresponding to the category_id. I am sorry I am new to python programming. I know I can hard code the dictionary and key values and go from there. However I was wondering if there is a way with python/pandas to do this in an easier way.

Answer 1

You can use pandas.Series.map() which maps values of Series according to input correspondence.

df1['tilte'] = df1['category_id'].map(df2.set_index('id')['title'])

# print(df1)

   category_id tags tilte
0            1    a  film
1            1    a  film
2           10    b   NaN
3           10    c   NaN
4           40    d   NaN