31 — Records: a small address book

A record is one dict with several fields. An address book is a list of those records saved as JSON. This guide builds a menu-driven book that adds a contact, lists everyone, and searches by name — each change saved to a file.

#Steps

1. One contact is a dict with a name and a phone. The whole book is a list of those dicts:

   mina = {"name": "Mina", "phone": "010-1234"}
   contacts = [mina]
   show f"{contacts[0]['name']}: {contacts[0]['phone']}"
   

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   Run it; it prints Mina: 010-1234. contacts[0] is the first dict and ['name'] picks the field out of it.

2. A real book loads a saved file, or begins empty when the file does not exist yet. Guide 15 used os.path.exists the same way:

   import os
   use file latest
   
   if os.path.exists("address.json"):
       contacts = json_load("address.json")
   else:
       contacts = []
   

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   json_load returns the whole list of dicts, exactly as it was saved.

3. add grows the list with append and writes it back. json_save accepts a list, not just a dict:

   contacts.append({"name": name, "phone": phone})
   json_save("address.json", contacts)
   

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4. list walks the list with a for loop and prints both fields of each record:

   for contact in contacts:
       show f"{contact['name']}: {contact['phone']}"
   

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5. search filters the same loop. find in contact["name"] is true when the typed text appears anywhere in the name, so Min finds Mina:

   for contact in contacts:
       if find in contact["name"]:
           show f"{contact['name']}: {contact['phone']}"
   

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6. The whole menu in one file. Save address.nme:

   # address.nme — a small address book in a JSON file.
   # Run: nme r address
   # Type add, list, search, or quit.
   
   import os
   use file latest
   
   # Load saved contacts, or start with an empty list.
   if os.path.exists("address.json"):
       contacts = json_load("address.json")
   else:
       contacts = []
   
   while True:
       show ""
       show "Commands: add, list, search, quit"
       ask command, "? "
       if command == "add":
           ask name, "Name? "
           ask phone, "Phone? "
           contacts.append({"name": name, "phone": phone})
           json_save("address.json", contacts)
           show f"Saved {name}: {phone}"
       elif command == "list":
           show f"{len(contacts)} contacts"
           for contact in contacts:
               show f"{contact['name']}: {contact['phone']}"
       elif command == "search":
           ask find, "Search? "
           for contact in contacts:
               if find in contact["name"]:
                   show f"{contact['name']}: {contact['phone']}"
       elif command == "quit":
           show "Bye!"
           break
       else:
           show "Unknown command"
   

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   Run it and feed the commands through a pipe:

   printf 'add\nMina\n010-1234\nlist\nsearch\nMin\nquit\n' | nme r address
   

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   Commands: add, list, search, quit
   ? Name? Phone? Saved Mina: 010-1234
   
   Commands: add, list, search, quit
   ? 1 contacts
   Mina: 010-1234
   
   Commands: add, list, search, quit
   ? Search? Mina: 010-1234
   
   Commands: add, list, search, quit
   ? Bye!
   

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   add saves the new contact to address.json; the next nme r address loads it back, so the book keeps its contacts between runs. while True: never ends on its own, so quit must break out — the menu shape from guide 22.

7. Korean writes the same menu with 파일 사용 최신, 물어봐, and json저장. The full Korean program is in the Korean guide; this snippet loads the saved book:

   파일 사용 최신
   if os.path.exists("address.json"):
       연락처 = json읽기("address.json")
   else:
       연락처 = []
   

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#Try it yourself

Add an email field to every contact: ask for it in add, save it in the dict, and print it in list. The saved JSON changes shape, and old files without the field still load — a missing field simply prints nothing.

#What you learned

• A record is a dict; a book is a list of dicts saved as JSON.
• json_save writes a list of dicts just like a single dict.
• while True: with a quit command and break makes a menu that never ends on its own.
• find in contact["name"] searches for text inside a field.
• os.path.exists lets the first run start with an empty list.