56 — Log: an event record

The diary in guide 35 writes one file per day. A log is the opposite: one growing file with a new line for every event, showing when things happened.

#Steps

1. Ask datetime for now and shape it as text. datetime.now() is this moment; strftime (guide 24) formats it — %Y year, %m month, %d day, %H hour, %M minute:

   from datetime import datetime
   now = datetime.now()
   stamp = now.strftime("%Y-%m-%d %H:%M")
   show stamp
   

   copyrun it →

2. file_write from guide 13 replaces the whole file, so appending means read the old log, add one line, write it all back:

   use file latest
   log = file_read("log.txt")
   file_write("log.txt", log + stamp + " - program started\n")
   

   copyrun it →

   Python's open(path, "a") appends in one call — the a means append — but the read-then-write way also lets the program read the log back for a menu.

3. The full logger appends a dated line on every add. The first run must not fail when log.txt does not exist, so os.path.exists starts empty. Save it as log.nme:

   # log.nme — a small event logger.
   # Run: nme r log
   
   use file latest
   from datetime import datetime
   import os
   if os.path.exists("log.txt"):
       log = file_read("log.txt")
   else:
       log = ""
   
   while True:
       ask choice, "(add, show, quit) "
       if choice == "add":
           ask event, "what happened? "
           stamp = datetime.now().strftime("%Y-%m-%d %H:%M")
           log = log + stamp + " - " + event + "\n"
           file_write("log.txt", log)
           show "saved: " + stamp + " - " + event
       elif choice == "show":
           show "log.txt has " + str(len(log.splitlines())) + " line(s):"
           for line in log.splitlines():
               show line
       else:
           show "bye"
           break
   

   copyrun it →

4. Run it twice, adding a different event each time — the second run shows the first event still there, the log growing across runs:

   printf 'add\nwater the plants\nshow\nquit\n' | nme r log
   printf 'add\ncall mom\nshow\nquit\n' | nme r log
   

   copy

   (add, show, quit) what happened? saved: 2026-08-11 14:05 - water the plants
   (add, show, quit) log.txt has 1 line(s):
   2026-08-11 14:05 - water the plants
   (add, show, quit) bye
   (add, show, quit) what happened? saved: 2026-08-11 14:05 - call mom
   (add, show, quit) log.txt has 2 line(s):
   2026-08-11 14:05 - water the plants
   2026-08-11 14:05 - call mom
   (add, show, quit) bye
   

   copy

   The timestamps are real — run it yourself and log.txt records the actual minute of each add.

#Try it yourself

Count events per day: change the timestamp to strftime("%Y-%m-%d"), then use the dict counting from guide 36 for how many lines share each date.

#What you learned

• datetime.now().strftime(format) shapes the current moment as text.
• Appending is read + one new line + file_write, because file_write replaces the whole file.
• open(path, "a") appends directly; with closes the file.
• os.path.exists lets the first run start with an empty log.