Question

所以我是Python的新手，现在我正在研究继承。我有一个名为LibraryItem的类名，里面装满了书和杂志，我已经使用它手动添加了它们

def new_book(self):
    self.libraryitems.append(Book("The Fault in Our Stars", "Fiction", "asdasd", "John Green", "012012", "D12"))

但是当我键入1来打印所有书籍时，它在CMD中不返回任何内容，而在IDLE中则无效。我的代码有什么问题吗？

当我想使用1显示库项目时：

def show_libraryitems(self, libraryitems=None):
    if not libraryitems:
        libraryitems = self.Catalog.libraryitems
    for Book in libraryitems:
        print("{0}: {1}\n{2}".format(libraryitem.title, libraryitem.subject))

这是完整的代码

这是菜单类

import sys
from LibraryItem import LibraryItem, Catalog, Book, Magazine, DVD

class Menu:
    '''Display a menu and respond to choices when run.'''
    def __init__(self):
        self.Catalog = Catalog()
        self.choices = {
                "1": self.show_libraryitems,
                "2": self.search_libraryitems,
                "3": self.quit
                }

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

1. Show all File
2. Search Library
3. 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_libraryitems(self, libraryitems=None):
        if not libraryitems:
            libraryitems = self.Catalog.libraryitems
        for libraryitem in libraryitems:
            print("{0}: {1}\n{2}".format(libraryitem.title, libraryitem.subject, libraryitem.contributor))

    def search_libraryitems(self):
        filter = input("Search for: ")
        libraryitems = self.Catalog.search(filter)
        self.show_libraryitems(libraryitems)

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

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

这是LibraryItem类

import datetime

last_id = 0

class LibraryItem:

    def __init__(self, title, subject, contributor=''):
        self.title = title
        self.subject = subject
        self.contributor = contributor


    def match(self, filter):
        return filter in self.title or filter in self.subject

class Book(LibraryItem):
    def __init__(self, title, subject, contributor, author, isbn, dds_number=''):
        super().__init__(title, subject, contributor)
        self.author = author
        self.isbn = isbn
        self.dds_number = dds_number


class Magazine(LibraryItem):
    def __init__(self, title, subject, contributor, volume, issue=''):
        super().__init__(title, subject, contributor)
        self.volume = volume
        self.issue = issue
class DVD(LibraryItem):
    def __init__(self, title, subject, contributor, actors, director, genre=''):
        super().__init__(title, subject, contributor)
        self.director = director
        self.genre = genre

class Catalog:

    def __init__(self):
        self.libraryitems = []

    def new_book(self):
        self.libraryitems.append(Book("The Fault in Our Stars", "Fiction", "asdasd", "John Green", "012012", "D12"))
    def new_magazine(self):
        self.libraryitems.append(Magazine("VOGUE", "lifestyle", "asdasd", "name", "asd"))

    def search(self, filter):
        return [libraryitem for libraryitem in self.libraryitems if
                    libraryitem.match(filter)]

Answer 1

在Python 2上，您应该使用raw_input，而不是input。自己尝试看看：

$ python2
Python 2.7.14 (default, Oct 31 2017, 21:12:13)
[GCC 6.4.0] on cygwin
Type "help", "copyright", "credits" or "license" for more information.
>>> x = input('blah: ')
blah: 1
>>> x
1
>>> type(x)
<type 'int'>

在Python 2上，input(...)接受您输入的字符串，（不幸的是）将其通过eval(...)传递，因此您将返回int而不是字符串。您可以自己测试一下，看看。

在Python 3上，input(...)与Python 2的raw_input(...)相同。在Python 2上，几乎不要使用input()；这被认为是Python 3中已纠正的错误。

也就是说，我很困惑，因为您的其余代码看起来像Python3。例如，不带参数的super()是Python 3语法。

为什么当我想在键入1

1 个答案: