2

I am trying out the set_index() method in Pandas but I get an exception I can not explain:

df

    movieId title        genres
1   2   Jumanji (1995)  Adventure|Children|Fantasy
5   6   Heat (1995) Action|Crime|Thriller
10  11  American President, The (1995)  Comedy|Drama|Romance

df.set_index(['a' , 'b' , 'c'], inplace = True)
df

KeyError: 'a'
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1 Answer 1

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1

If want set index by nested list (double []) with same length as df:

df.set_index([['a' , 'b' , 'c']], inplace = True)
print (df)
   movieId                          title                      genres
a        2                 Jumanji (1995)  Adventure|Children|Fantasy
b        6                    Heat (1995)       Action|Crime|Thriller
c       11  American President The (1995)        Comedy|Drama|Romance

If use list ([]) pandas try set columns a,b,c to MultiIndex and because does not exist error is raised.

So if want set index by columns:

df.set_index(['movieId' , 'title'], inplace = True)
print (df)
                                                           genres
movieId title                                                    
2       Jumanji (1995)                 Adventure|Children|Fantasy
6       Heat (1995)                         Action|Crime|Thriller
11      American President The (1995)        Comedy|Drama|Romance
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