66 — Top ten: ranking records

Guide 39 sorted plain numbers and guide 54 summarized them. Real data is a list of records, each a dict with several fields; ranking them means sorting by one field — a score. This guide loads records from JSON, sorts them by score with sorted(..., key=...), and shows the top ten with a slice.

#Steps

1. Create records.json with at least twelve records. Each record is a dict with a name and a numeric score:

   [
     {"name": "Mina", "score": 88},
     {"name": "Jun", "score": 95},
     {"name": "Sora", "score": 72},
     {"name": "Ravi", "score": 91},
     {"name": "Lena", "score": 84},
     {"name": "Tom", "score": 67},
     {"name": "Aya", "score": 79},
     {"name": "Ben", "score": 93},
     {"name": "Kim", "score": 58},
     {"name": "Nia", "score": 86},
     {"name": "Leo", "score": 74},
     {"name": "Sam", "score": 90}
   ]
   

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2. Load the list with json_load from guide 14:

   use file latest
   records = json_load("records.json")
   show f"loaded {len(records)} records"
   

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   It prints loaded 12 records.

3. sorted needs to know which field to compare, because a whole dict has no natural order. The key argument supplies that field: lambda r: r["score"] is a tiny function that takes a record r and returns its score. reverse=True puts the highest score first:

   records = [{"name": "Mina", "score": 88}, {"name": "Jun", "score": 95}]
   top = sorted(records, key=lambda r: r["score"], reverse=True)
   show top
   

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   [{'name': 'Jun', 'score': 95}, {'name': 'Mina', 'score': 88}]
   

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   Jun ranks first because 95 beats 88 — the dicts are compared by score, not by name.

4. [:10] keeps the first ten entries of a list — the top ten. Slicing works on numbers and records alike:

   scores = [5, 2, 9, 1, 7, 3]
   top = sorted(scores, reverse=True)[:3]
   show top
   

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   [9, 7, 5]
   

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5. The full program loads the records, sorts them by score, prints the top ten with a rank number, and shows who barely missed the cut. Save top-ten.nme:

   # top-ten.nme — the ten highest scores from records.json.
   # Run: nme r top-ten
   # The file records.json must exist in the same folder.
   
   use file latest
   
   records = json_load("records.json")
   show f"loaded {len(records)} records"
   
   top = sorted(records, key=lambda r: r["score"], reverse=True)[:10]
   
   show "top ten:"
   rank = 1
   for r in top:
       show f"  {rank}. {r['name']}: {r['score']}"
       rank = rank + 1
   
   all_ranked = sorted(records, key=lambda r: r["score"], reverse=True)
   just_missed = all_ranked[10]
   show f"just missed: {just_missed['name']}: {just_missed['score']}"
   

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   The rank counter starts at 1 and grows inside the loop, so line 1 is the best score and line 10 the lowest of the ten. all_ranked[10] reads the eleventh entry — index 10 counts from 0, so it is the first record outside the top ten.

6. Run it with the data file present:

   nme r top-ten
   

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   loaded 12 records
   top ten:
     1. Jun: 95
     2. Ben: 93
     3. Ravi: 91
     4. Sam: 90
     5. Mina: 88
     6. Nia: 86
     7. Lena: 84
     8. Aya: 79
     9. Leo: 74
     10. Sora: 72
   just missed: Tom: 67
   

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   Tom (67) is the 11th-highest score and Kim (58) the 12th. sorted ordered all twelve by score; [:10] dropped the last two.

7. Korean writes the same steps with 파일 사용 최신, json읽기, and 말해; the full Korean program is in the Korean guide.

#Try it yourself

Add a thirteenth record with a high score and rerun — the weakest of the ten drops off and the new one appears. Or use [:5] for a top five, or change reverse=True to False to show the bottom ten.

#What you learned

• Records are dicts; sorted needs a key to compare one field.
• lambda r: r["score"] is a tiny function that returns a record's score.
• sorted(records, key=..., reverse=True) ranks the highest score first.
• [:10] slices the sorted list down to the top ten.