Question

我正在尝试打印对象（记录）的列表（电话簿），但是我是python的新手，并且它无法识别记录是列表中的对象。在这种情况下如何调用对象？

我尝试查看python的循环教程，但没有一个参考如何调用列表中的对象。

class record:
    def __init__(self,telephone,lastname,firstname):
        self.telephone = telephone
        self.lastname = lastname
        self.firstname = firstname

class PhoneBook:
    def __init__(self):
        self.phonebook = []

    def printphonebook(self):
        for record in self.phonebook:
            x = 0
            print(self.phonebook[x])
            x = x + 1

预期的输出将是对象列表，包括电话号码，姓氏和名字。

Answer 1

您要打印类的实例。因此，您应该提供特殊的__str__方法来告诉python如何打印对象。 __str__()必须返回一个字符串：here文档。

class record:
    def __init__(self,telephone,lastname,firstname):
        self.telephone = telephone
        self.lastname = lastname
        self.firstname = firstname

    def __str__(self):
        #returning a string with the content, you can edit the string to fit your needs.
        #here I am using formatted string literals, works with python >= 3.6
        return f"Last name: {self.lastname}, First Name: {self.firstname}, Telephone: {self.telephone}"

class PhoneBook:
    def __init__(self):
        self.phonebook = []

    def printphonebook(self):
        for entry in self.phonebook:
            print(entry)

这里发生的是，当您调用print(record)时，__str__()方法用于提供表示实例内容的字符串。

因此，如果您这样做：

book = PhoneBook()
book.phonebook.append(record(800, "Wayne", "Bruce"))
book.phonebook.append(record(1234,  "Kent", "Clark"))
book.phonebook.append(record(499, "Prince", "Diana"))

book.printphonebook()

这将打印：

姓氏：Wayne，名字：Bruce，电话：800
  姓氏：Kent，名字：Clark，电话：1234
  姓：Prince，名字：Diana，电话：499

Answer 2

您的self.phonebook中没有元素。当然，它什么也不打印。
每次创建x=0的迭代，因此您始终将打印第一项：

class record:
    def __init__(self,telephone,lastname,firstname):
        self.telephone = telephone
        self.lastname = lastname
        self.firstname = firstname

class PhoneBook:
    def __init__(self):
        self.phonebook = [1,2,3,4,5]

    def printphonebook(self):
        for record in self.phonebook:
            x = 0
            print(self.phonebook[x])
            x = x + 1

a = PhoneBook()
a.printphonebook()

您的x索引确实毫无意义，您只需打印record：

class record:
    def __init__(self,telephone,lastname,firstname):
        self.telephone = telephone
        self.lastname = lastname
        self.firstname = firstname

class PhoneBook:
    def __init__(self):
        self.phonebook = [1,2,3,4,5]

    def printphonebook(self):
        for record in self.phonebook:
            print(record)

a = PhoneBook()
a.printphonebook()

因此：1.用任何元素填充self.phonebook。2.打印record，不带索引。

如何遍历对象列表

2 个答案: