Python面向对象编程 - 一个记事本程序范例(一)

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=''):
        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):
        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 a 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 note.id == 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.'''
        self._find_note(note_id).memo = memo

    def modify_tags(self, note_id, tags):
        '''Find the note with the given id and change its
        tags to the given value.'''
        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)]

from notebook import Note, Notebook

def display_notes(notes):
    for note in notes:
        print("Id: %d" %(note.id))
        print("Memo: %s" %(note.memo))
        print("------------------------------------------")

n = Notebook()
n.new_note("hello world")
n.new_note("hello again")
print(n.notes)
display_notes(n.notes)

print("********************************************")
print("search keyword: hello")
search_notes = n.search("hello")
display_notes(search_notes)
print("********************************************")

print("********************************************")
print("search keyword: world")
search_notes = n.search("world")
display_notes(search_notes)
print("********************************************")

print("********************************************")
print("after modify note 1:")
n.modify_memo(1, "Hi Master HaKu")
display_notes(n.notes)
print("********************************************")