For each value in list of dictionaries print corresponding value in python

Question

I have a list of dictionaries and I want to do a for each to find corresponding values.

My list:

my_list = [{'genre':'Dystopia', 'book':'Hunger Games'},
           {'genre':'Fanstasy', 'book':'Harry Potter'},
           {'genre':'Dystopia', 'book':'Divergent'}]

I want to get books corresponding to the genre.

Expected result:

for 'Dystopia' get 'Hunger Games', 'Divergent'
for 'Fantasy' get 'Harry Potter'

I am not sure how to go about it. I know I need a for loop but don't know what to do beyond that.

for x in my_list:
   x['url']

Not sure what to add next.

What is the issue, exactly? That for loop looks fine to me. Why are you using a list of dictionaries for this? — AMC, Jan 16 '20 at 17:03

cmxu · Accepted Answer · 2020-01-16T15:10:57.833

1

Try this.

[dictionary['book'] for dictionary in my_list if dictionary['genre'] == 'Dystopia']

This goes through all of the dictionaries in my_list and if the genre is Dystopia it records the book.

Below shows how to obtain a dictionary that contains all books for each genre.

genres = set([dictionary['genre'] for dictionary in my_list])
result = {genre:[dictionary['book'] for dictionary in my_list if dictionary['genre'] == genre] for genre in genres}

edited Jan 16 '20 at 15:10

answered Jan 16 '20 at 15:05

cmxu

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I have multiple genres and want to avoid hard coding values like Dystopia. I just wanted it to return the value for each of the genres – nb_nb_nb Jan 16 '20 at 15:08

Adam.Er8 · Answer 2 · 2020-01-16T15:14:15.617

0

you want to get a dictionary of genre -> list of books,

so you need to iterate my_list, take the genre (as the key) and the book (as the value) and append it to the list of books in this genre

using defaultdict will easily eliminate the corner case of the first book.

from collections import defaultdict

result = defaultdict(list)
for d in my_list:
  result[d['genre']].append(d['book'])

edited Jan 16 '20 at 15:14

answered Jan 16 '20 at 15:08

Adam.Er8

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score 0 · Answer 3 · answered Jan 16 '20 at 15:11

Hi please find the solution below.

my_list = [
{'genre':'Dystopia', 'book':'Hunger Games'},
           {'genre':'Fanstasy', 'book':'Harry Potter'},
           {'genre':'Dystopia', 'book':'Divergent'}
           ]
genre_holder = dict()
for item in my_list:
    if genre_holder.get(item['genre'],"empty") == "empty":
         genre_holder[item['genre']] = list()
    genre_holder[item['genre']].append(item['book'])
print(genre_holder)

for genre in genre_holder:
    print("for ",genre," get ", ",".join(genre_holder[genre]))

Johan Dettmar · Answer 4 · 2020-01-16T17:18:42.200

0

For a more functional approach, this return a map of the correct books:

list(map(lambda x: x["book"], filter(lambda x: x["genre"] == "Dystopia", my_list)))
>>> ['Hunger Games', 'Divergent']

edited Jan 16 '20 at 17:18

answered Jan 16 '20 at 15:15

Johan Dettmar

27,968
5
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score 0 · Answer 5 · answered Jan 16 '20 at 15:16

You could do something like this:

books={}
for i in my_list:
    genre=i["genre"]
    book=i["book"]
    if genre in books:
        if book in books[genre]:
            continue
    else:
        books[genre]=[]
    books[genre].append(book)

print(books)

output

{'Dystopia': ['Hunger Games', 'Divergent'], 'Fanstasy': ['Harry Potter']}

score 0 · Answer 6 · answered Jan 16 '20 at 15:18

From this answer, you could try to create a new class from built-in dict:

class Dictlist(dict):
    def __setitem__(self, key, value):
        try:
            self[key]
        except KeyError:
            super(Dictlist, self).__setitem__(key, [])
        self[key].append(value)

So...

d = Dictlist()
for element in my_list:
    d[element['genre']] = d['book']

output:

{'Dystopia': ['Hunger Games', 'Divergent'], 'Fanstasy': ['Harry Potter']}

For each value in list of dictionaries print corresponding value in python

6 Answers6