53 — Sets: unique values

Guide 36 counted every word, repeats and all. A set keeps only the unique values, so set(words) answers a different question: how many different words are there?

#Steps

1. Create a small text file, story.txt, next to your program:

   the quick brown fox jumps over the lazy dog
   the fox and the dog are friends
   quick and lazy are fun words to say
   

   copyrun it →

2. Read it and split it (guide 36); set(words) drops the repeats, so len(set(words)) counts the different words:

   use file latest
   text = file_read("story.txt")
   words = text.split()
   show f"total words: {len(words)}"
   show f"different words: {len(set(words))}"
   

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   The story has 24 words but only 15 different ones. A set has no order and no repeats, so the same word can never sit inside twice.

3. Sets have no positions, so my_set[0] fails. sorted(...) (guide 39) converts one back to an ordered list, and in checks membership:

   unique_words = set(["the", "dog", "the", "cat"])
   for word in sorted(unique_words):
       show "  " + word
   show f"dog present? {'dog' in unique_words}"
   

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   It prints cat, dog, the — alphabetical, each once — then True.

4. Strings become sets of characters too, and the space counts as a member:

   letters = set("hello world")
   show sorted(letters)
   

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   It prints [' ', 'd', 'e', 'h', 'l', 'o', 'r', 'w'] — eight members.

5. The full program reads the story, builds both sets, and reports them. Save sets.nme:

   # sets.nme — sets keep only unique values.
   # Run: nme r sets
   # The file story.txt must exist in the same folder.
   
   use file latest
   
   text = file_read("story.txt")
   words = text.split()
   
   show f"total words in story.txt: {len(words)}"
   
   unique_words = set(words)
   show f"different words: {len(unique_words)}"
   show ""
   
   show "the different words, sorted:"
   show sorted(unique_words)
   
   show f"is 'fox' in the story? {'fox' in unique_words}"
   show f"is 'zebra' in the story? {'zebra' in unique_words}"
   show ""
   
   sentence = "hello world"
   letters = set(sentence)
   show f"sentence: {sentence}"
   show f"members inside set(sentence): {len(letters)}"
   show sorted(letters)
   
   show ""
   show "list vs set:"
   show f"  list length (with repeats): {len(words)}"
   show f"  set length (no repeats):   {len(unique_words)}"
   

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   Run nme r sets with story.txt in the folder:

   total words in story.txt: 24
   different words: 15
   
   the different words, sorted:
   ['and', 'are', 'brown', 'dog', 'fox', 'friends', 'fun', 'jumps', 'lazy', 'over', 'quick', 'say', 'the', 'to', 'words']
   is 'fox' in the story? True
   is 'zebra' in the story? False
   
   sentence: hello world
   members inside set(sentence): 8
   [' ', 'd', 'e', 'h', 'l', 'o', 'r', 'w']
   
   list vs set:
     list length (with repeats): 24
     set length (no repeats):   15
   

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   The list holds every word; the set holds one copy of each. Membership checks use the same in a dict uses for keys.

6. Korean writes the same program with 파일 사용 최신, 파일읽기, and 말해; the full Korean program is in the Korean guide.

#Try it yourself

Add a line to story.txt that reuses an old word, like the dog and the fox jump; the total word count grows, but the different-word count may not. Then build a letter set from your own name with set("your name") and count it.

#What you learned

• set(words) keeps one copy of each value, with no order and no repeats.
• len(set(...)) counts the different values, not all of them.
• sorted(a_set) converts the set back into an ordered list.
• 'fox' in a_set asks whether a value is inside, like a dict's keys.
• set("hello world") works on a string, where the space is a member too.