Python OOP的例子：Notebook

1、notebook.py

import datetime

last_id = 0


class Note:
    """Represent a note in the notebook. Match against a
    string in searches and store tags for each note."""

    def __init__(self, memo, tags=''):
        """initialize a note with memo and optional
        space-separated tags. Automatically set the note's
        creation date and a unique id."""
        self.memo = memo
        self.tags = tags
        self.creation_date = datetime.date.today()
        global last_id
        last_id += 1
        self.id = last_id

    def match(self, filter):
        """Determine if this note matches the filter
        text. Return True if it matches, False otherwise.

        Search is case-sensitive and matches both text and tags."""

        return filter in self.memo or filter in self.tags


class Notebook:
    """Represent a collection of notes that can be tagged,
    modified, and searched."""

    def __init__(self):
        """Initialize a notebook with an empty list."""
        self.notes = []

    def new_note(self, memo, tags=''):
        """Create aa new note and add it to the list."""
        self.notes.append(Note(memo, tags))

    def _find_note(self, note_id):
        """Locate the note with the given id."""
        for note in self.notes:
            if str(note.id) == str(note_id):
                return note
            return None

    def modify_memo(self, note_id, memo):
        """Find the note with the given id and change its
        memo to the given value."""
        # for note in self.notes:
        #     if note.id == note_id:
        #         note.memo = memo
        #         break
        note = self._find_note(note_id)
        if note:
            note.memo = memo
            return True
        return False

    def modify_tags(self, note_id, tags):
        """Find the note with the given id and change its
        tags to the given value."""
        # for note in self.notes:
        #     if note.id == note_id:
        #         note.tags = tags
        #         break
        self._find_note(note_id).tags = tags

    def search(self, filter):
        """Find all notes that match the given filter string."""
        return [note for note in self.notes if note.match(filter)]

2.menu.py

import sys
from notebook import Notebook, Note


class Menu:
    """Display a menu and respond to choices when run."""
    def __init__(self):
        self.notebook = Notebook()
        self.choices = {
            "1": self.show_notes,
            "2": self.search_notes,
            "3": self.add_note,
            "4": self.modify_note,
            "5": self.quit
        }

    def display_menu(self):
        print("""
Notebook Menu

1.Show all Notes
2.Search Notes
3.Add Note
4.Modify Note
5.Quit        
        """)

    def run(self):
        """Display the menu and respond to choices."""
        while True:
            self.display_menu()
            choice = input("Enter an option:")
            action = self.choices.get(choice)
            if action:
                action()
            else:
                print("{0} is not a valid choice.".format(choice))

    def show_notes(self, notes=None):
        if not notes:
            notes = self.notebook.notes
        for note in notes:
            print("{0}: {1}\n{2}".format(note.id, note.tags, note.memo))

    def search_notes(self):
        filter = input("Search for:")
        notes = self.notebook.search(filter)
        self.show_notes(notes)

    def add_note(self):
        memo = input("Enter a memo:")
        tags = input("Enter tags:")
        self.notebook.new_note(memo, tags=tags)
        print("Your note has been added.")

    def modify_note(self):
        id = input("Enter a note id::")
        memo = input("Enter a memo::")
        tags = input("Enter tags::")
        if memo:
            self.notebook.modify_memo(id, memo)
        if tags:
            self.notebook.modify_tags(id, tags)

    def quit(self):
        print("Thank you for using your notebook today.")
        sys.exit(0)


if __name__ == '__main__':
    Menu().run()