CODEWITHSUNDEEP
python
Arjun Chakraborty
Arjun Chakraborty

Reputation: 11

Nested list sort

How do I append two values to a key in dictionary

It is throwing error str object has no attribute append

score_list={}
for _ in range(int(input())):
    score=float(input())
    name=input()
    if score in score_list:
        score_list[score].append(name)
    else:
        score_list[score]=name
new_list=[]
for score in score_list:
    new_list.append([score,score_list[score]])
new_list.sort()

Upvotes: 1

Views: 108

Answers (2)

Patrick Artner
Patrick Artner

Reputation: 51643

You need to add a list to your dict - not the string directly. Three ways I know of, from worst to best.

You can either use a normal dict and change your code to 

score_list={}
for _ in range(int(input())):
    score=float(input())
    name=input()
    if score in score_list:
        score_list[score].append(name)
    else:

        score_list[score] = [name]  # add as 1-elem list

or use dict.setdefault(key,defaultvalue):

score_list={}
for _ in range(int(input())):
    score=float(input())
    name=input()

    k = score_list.setdefault(score,[]) # create key if needed with empty list
    k.append(name)

or use a collections.defaultdict(list).

score_list=defaultdict(list)

for _ in range(int(input())):
    score=float(input())
    name=input()

    score_list[score].append(name)  # defaultdict handles list creation for you

The last method is most performant - setdefault(score,[]) creates lots of empty default-lists that are not used if the key already exists.

If you need a top n result, you can create it directly from the dictionaries item()s:

n = 5
top_n = sorted(score_list.items(), reverse=True) [:n]  # sorts by max score first 
# top_n  is a list of tuples:  [ (10000,["a","b","c"]) , (9999, ["b"]), ... ]

Upvotes: 5

Dani Mesejo
Dani Mesejo

Reputation: 61910

If I understood correctly, you need to change the line:

score_list[score]=name

to:

score_list[score]=[name]

In your current version you are assigning the string name to score_list[score], so you need to change to a list hence the change.

Upvotes: 2

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