python编程：迭代对象、Iterator迭代器、生成器

# -*- coding: utf-8 -*-
# @File    : 迭代器模式.py
# @Date    : 2018-05-23
from abc import abstractmethod
# 定义迭代器
# 实现了两个方法，是否还有未被访问的元素和下一个未被访问的元素
class Iterator(object):
    def __init__(self):
        pass
    @abstractmethod
    def has_next(self):
        pass
    @abstractmethod
    def next(self):
        pass
# 一个书架上摆满了书，我们需要查找某本书时，就用到了迭代器模式
# 定义书本， 名称和编号
class Book(object):
    def __init__(self, name, number):
        self.name = name
        self.number = number
# 书架定义
# 书架实现了增加书目，查找index位置的数目以及总共的图书数目这几个方法
class BookShelf(object):
    def __init__(self):
        self.books = []
    def append_book(self, book):
        self.books.append(book)
    def get_book_at(self, index):
        return self.books[index]
    def get_length(self):
        return self.books.__len__()
# Iterator的具体实现
class BookShelfIterator(Iterator):
    def __init__(self, book_shelf):
        self.book_shelf = book_shelf
        self.index = 0
    def has_next(self):
        if self.index < self.book_shelf.get_length():
            return True
        else:
            return False
    def next(self):
        book = self.book_shelf.get_book_at(self.index)
        self.index += 1
        return book
if __name__ == "__main__":
    book_shelf = BookShelf()
    book_shelf.append_book(Book("语文", "001"))
    book_shelf.append_book(Book("数学", "002"))
    book_shelf.append_book(Book("英语", "003"))
    book_shelf_iterator = BookShelfIterator(book_shelf)
    # 通过hasNext方法和next方法便可以访问数目的具体信息
    while book_shelf_iterator.has_next():
        book = book_shelf_iterator.next()
        print(book.name, book.number)
"""
语文 001
数学 002
英语 003
"""

# 新书架python实现
class NewBookShelf(BookShelf):
    def __init__(self):
        self.index = 0
        BookShelf.__init__(self)
    # 实现容器，进行成员检查
    def __contains__(self, book):
        if book in self.books:
            return True
        else:
            return False
    # 可迭代对象实现了__iter__方法
    def __iter__(self):
        return self
    #  迭代器实现next方法
    def __next__(self):
        if self.index < self.get_length():
            book = self.books[self.index]
            self.index += 1
            return book
        else:
            raise StopIteration # 停止标志
if __name__ == "__main__":
   # 新书架
    new_book_shelf = NewBookShelf()
    book1 =Book("语文", "001")
    new_book_shelf.append_book(book1)
    new_book_shelf.append_book(Book("数学", "002"))
    new_book_shelf.append_book(Book("英语", "003"))
    # 成员检查
    print(book1 in new_book_shelf)
  # True
    # 迭代书本
    for book in new_book_shelf:
        print(book.name, book.number)
"""
语文 001
数学 002
英语 003
"""

# 新书架python实现
class NewBookShelf(BookShelf):
    def __init__(self):
        self.index = 0
        BookShelf.__init__(self)
    # 实现容器，进行成员检查
    def __contains__(self, book):
        if book in self.books:
            return True
        else:
            return False
    # 可迭代对象实现了__iter__方法
    def __iter__(self):
        return self
    def next(self):
        if self.index < self.get_length():
            book = self.books[self.index]
            self.index += 1
            return book
        else:
            raise StopIteration  # 停止标志

TypeError: iter() returned non-iterator of type 'NewBookShelf'

# 新书架python实现
class NewBookShelf(BookShelf):
    def __init__(self):
        self.index = 0
        BookShelf.__init__(self)
    # 实现容器，进行成员检查
    def __contains__(self, book):
        if book in self.books:
            return True
        else:
            return False
    # 可迭代对象实现了__iter__方法
    def __iter__(self):
        return self
  # 兼容 Python3 和 Python2
    def next(self):
        return self.__next__()
    #  迭代器实现next方法
    def __next__(self):
        if self.index < self.get_length():
            book = self.books[self.index]
            self.index += 1
            return book
        else:
            raise StopIteration  # 停止标志