3

I'm trying to sort by level first, followed by reviews. The dataframe dtype are all str.

ranking_level_sort = {
    "Exceptional": 5,
    "Excellent": 4,
    "Very good": 3,
    "Good": 2,
    "Review score": 1,
    "None": 0
}

hotel_sorted = hotel.sort_values(by=["level", "reviews"],  key=lambda x: x.map(ranking_level_sort), ascending=[False, False])
hotel_sorted.reset_index(drop=True, inplace=True)
hotel_sorted

What I Got

name price level reviews
Miniinn - Double Room with Private Bathroom 47 Exceptional 1
The Empire Brunei 309 Excellent 1464
Higher Hotel 24 Excellent 865
Radisson Hotel Brunei 120 Excellent 1314
Abdul Razak Hotel Apartment 59 Excellent 129

What I Expect

name price level reviews
Miniinn - Double Room with Private Bathroom 47 Exceptional 1
The Empire Brunei 309 Excellent 1464
Radisson Hotel Brunei 120 Excellent 1314
Higher Hotel 24 Excellent 865
Abdul Razak Hotel Apartment 59 Excellent 129

So far, I've managed to sort by level, and is not followed by reviews. The key argument in sort_values can only take one lambda expression. I'm not sure how this can be solved, any pointers?

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1
  • Very good question - code, sample data and expected ouput. Commented Sep 17, 2021 at 7:07

2 Answers 2

Reset to default
3

The map is applied for both columns. It finds no matches for reviews and returns NaN values. So you need to replace those by the original values using fillna, like this:

hotel_sorted = hotel.sort_values(by=["level", "reviews"],  
                                 key=lambda x: x.map(ranking_level_sort).fillna(x), 
                                 ascending=False)
hotel_sorted.reset_index(drop=True, inplace=True)

print (hotel_sorted)
                                          name  price        level  reviews
0  Miniinn - Double Room with Private Bathroom     47  Exceptional        1
1                            The Empire Brunei    309    Excellent     1464
2                        Radisson Hotel Brunei    120    Excellent     1314
3                                 Higher Hotel     24    Excellent      865
4                  Abdul Razak Hotel Apartment     59    Excellent      129
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1 Comment

@Michel de Ruiter - thank you very much.
3

Simple fix to your code (makes mapping apply to 'level' series only):

hotel_sorted = hotel.sort_values(by=["level", "reviews"],  
       key=lambda x: x if x.name!='level' else x.map(ranking_level_sort), 
       ascending=[False, False])
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