Question

I’m trying to print the list created by the functions in this class- what do I need to fix? I’m getting output from the terminal along the lines of [<__main__.Person instance at 0x1004a0320>,.

class Person:
    def __init__(self,first,last,id,email):
        self.firstName=first
        self.lastName=last
        self.id=id
        self.email=email
        self.friends=[]
    def add_friend(self,friend):
        if len(self.friends)<5:
            self.friends.append(friend)
        if len(friend.friends)<5:
            friend.friends.append(self)

p1=Person("David","Waver","922-43-9873","[e-mail]")
p2=Person("Bob","Jones","902-38-9973","[e-mail]")
p3=Person("James","Smith","302-38-9103","[e-mail]")
p4=Person("Tim","Jack","902-38-0918","[e-mail]")
p5=Person("Jim","Johnston","314-78-2343","[e-mail]")
p6=Person("Gina","Relent","102-38-1064","[e-mail]")
p7=Person("Greg","Morris","932-38-4473","[e-mail]")

p1.add_friend(p2)
p1.add_friend(p3)
p1.add_friend(p4)
p1.add_friend(p5)
p1.add_friend(p6)
p1.add_friend(p7)

print p1.friends

Answer 1

You need to define __repr__ or __str__ in your Person class.

>>> class Person:
...     def __init__(self,first,last,id,email):
...         self.firstName=first
...         self.lastName=last
...         self.id=id
...         self.email=email
...         self.friends=[]
...     def add_friend(self,friend):
...         if len(self.friends)<5:
...             self.friends.append(friend)
...         if len(friend.friends)<5:
...             friend.friends.append(self)
...     def __repr__(self):
...         return self.firstName + ' ' + self.lastName

Then initialize the list as above…

>>> print p1.friends
[Bob Jones, James Smith, Tim Jack, Jim Johnston, Gina Relent]

This answer gives a good explanation of these functions.

Given the above post’s point about the functions of __repr__ and __str__, probably the __repr__ should look more like this:

def __repr__(self):
    template = "Person('{0}', '{1}', '{2}', '{3}')"
    return template.format(self.firstName, self.lastName, self.id, self.email)

What’s nice about the above is that it generates a string that, when evaluated, creates an object that has the same properties (apart from friends) as the original. For example:

>>> print p1
Person('David', 'Waver', '922-43-9873', '[e-mail]')
>>> Person('David', 'Waver', '922-43-9873', '[e-mail]')
Person('David', 'Waver', '922-43-9873', '[e-mail]')