创建类方法 __str__

Question

I am working on a program that needs a str method. However, when I run the code, it only outputs:

What is the name of the pet: Tim
What type of pet is it: Turtle
How old is your pet: 6

How can I print out what I need from the str method? Here is what I have. This is the code for my class (classPet.py)

class Pet:
def __init__(self, name, animal_type, age):
    self.__name = name
    self.__animal_type = animal_type
    self.__age = age

def set_name(self, name):
    self.__name = name

def set_type(self, animal_type):
    self.__animal_type = animal_type

def set_age(self, age):
    self.__age = age

def get_name(self):
    return self.__name

def get_animal_type(self):
    return self.__animal_type

def get_age(self):
    return self.__age

def __str__(self):
    return 'Pet Name:', self.__name +\
           '\nAnimal Type:', self.__animal_type +\
           '\nAge:', self.__age

This is the code for my main function (pet.py):

import classPet

def main():
    # Prompt user to enter name, type, and age of pet
    name = input('What is the name of the pet: ')
    animal_type = input('What type of pet is it: ')
    age = int(input('How old is your pet: '))

    pets = classPet.Pet(name, animal_type, age)
    print()

main()

Answer 1

In the code for your main function (pet.py), you are calling print without any parameters. You need to call print with your pet instance as a parameter:

pets = classPet.Pet(name, animal_type, age)
print(pets)  # see here

You also need to fix an error in your __str__ method: the __str__ method doesn't concatenate all of its arguments to a string like the print() function does it. Instead, it must return a single string.

In your __str__ method you are seperating your different parts of the string by commas. This will make python think that it's dealing with a tuple. I propose the following solution using pythons format function:

def __str__(self):
    return "Pet Name: {}\nAnimal Type: {}\nAge: {}".format(self.__name, self.__animal_type, self.__age)

The {} parts in the string are placeholders that are replaced with the arguments in the parenthesis through the format function. They are replaced in order, so the first one is replaced with self.__name , etc.