65 — Files: processing many files

Guide 13 read one file you named in the code. Real folders hold many files, and you usually do not know their names ahead of time. os.listdir(".") lists every name in a folder, and file_read from guide 13 reads whichever one you point at. Together they turn a whole folder into a list you can loop over.

#Steps

1. Create two small text files next to your program. one.txt:

   the cat sat on the mat
   the dog ran past the cat
   

   copyrun it →

   And two.txt:

   a bird sang on the roof
   

   copyrun it →

2. import os loads Python's folder tools, and os.listdir(".") returns a list of every name in the current folder — . means "this folder". Count the list with len:

   import os
   names = os.listdir(".")
   show f"{len(names)} names in this folder"
   

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   With the program and the two text files, that prints 3 names in this folder. The list contains every name, including files-folder.nme — not just the text files.

3. .endswith(".txt") keeps only the text files. A for loop reads each kept name with file_read and splits it into words, exactly as guide 36 did for one file:

   import os
   use file latest
   for name in os.listdir("."):
       if name.endswith(".txt"):
           words = file_read(name).split()
           show f"{name}: {len(words)} words"
   

   copyrun it →

   two.txt: 6 words
   one.txt: 12 words
   

   copy

4. Letters count the same way per file: remove the spaces and the line breaks, then take len:

   use file latest
   text = file_read("one.txt")
   letters = len(text.replace(" ", "").replace("\n", ""))
   show letters
   

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   one.txt has 36 letters.

5. The full program collects the .txt names first, reports each file, and then the totals and the biggest file across all of them. Save files-folder.nme:

   # files-folder.nme — words and letters across every .txt file.
   # Run: nme r files-folder
   # Create one.txt and two.txt in the same folder first.
   
   import os
   use file latest
   
   files = os.listdir(".")
   txt_files = []
   for name in files:
       if name.endswith(".txt"):
           txt_files.append(name)
   
   show f"{len(txt_files)} txt files found:"
   
   total_words = 0
   total_letters = 0
   biggest = ""
   biggest_words = 0
   for name in txt_files:
       text = file_read(name)
       words = text.split()
       letters = len(text.replace(" ", "").replace("\n", ""))
       total_words = total_words + len(words)
       total_letters = total_letters + letters
       if len(words) > biggest_words:
           biggest_words = len(words)
           biggest = name
       show f"  {name}: {len(words)} words, {letters} letters"
   
   show "all files:"
   show f"  words: {total_words}"
   show f"  letters: {total_letters}"
   show f"  biggest: {biggest} with {biggest_words} words"
   

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   The if len(words) > biggest_words: check remembers the file with the most words, the same "best so far" idea as the high score in guide 15.

6. Run it with the two text files in the folder:

   nme r files-folder
   

   copy

   2 txt files found:
     two.txt: 6 words, 18 letters
     one.txt: 12 words, 36 letters
   all files:
     words: 18
     letters: 54
     biggest: one.txt with 12 words
   

   copy

   The program never names a file in advance: os.listdir found them, the if kept the .txt ones, and the totals add the per-file counts.

7. Korean writes the same steps with import os, 파일 사용 최신, and 파일읽기; the full Korean program is in the Korean guide.

#Try it yourself

Add a third file three.txt and rerun — it appears in the report with no code change. Or change the filter to if name.endswith(".csv"): and count lines instead of words: text.splitlines().

#What you learned

• os.listdir(".") returns every name in the current folder as a list.
• .endswith(".txt") filters the list to the files you want.
• file_read(name) reads the file named by any string, not just a literal.
• A for loop over a folder turns one-file handling into many-file handling.