How do I print this class variable? [duplicate]

Question

If I try to print the class variable which is a list, I get a Python object. (These are examples I found on stackoverflow).

 class Contacts:
    all_contacts = []

    def __init__(self, name, email):
       self.name = name
       self.email = email
       Contacts.all_contacts.append(self)

    def __str__(self):
       return '%s, <%s>' % (self.name, self.email)

c1 = Contacts("Grace", "[email protected]")
print(c1.all_contacts)

[<__main__.Contact object at 0x0287E430>, <__main__.Contact object`

But in this more simple example, it actually prints:

class Example():
    samplelist= [1,2,3]

test= Example()
print (test.samplelist)
[1, 2, 3]

I figured this line is the culprit: Contact.all_contacts.append(self) in the first sample code. But I'm not exactly sure whats going on here.

EDIT:

Several users told me to just append self.name instead of just self.

So when I do this:

class Contacts:
   all_contacts = []

   def __init__(self, name, email):
      self.name = name
      self.email = email
      Contacts.all_contacts.append(self.name)
      Contacts.all_contacts.append(self.email)

   def __str__(self):
      return '%s, <%s>' % (self.name, self.email)

   def __repr__(self):
      return str(self)

c1 = Contacts("Paul", "[email protected]")
c2 = Contacts("Darren", "[email protected]")
c3 = Contacts("Jennie", "[email protected]")

print(Contacts.all_contacts)

I get:

['Paul', '[email protected]', 'Darren', '[email protected]', 'Jennie', '[email protected]']

Instead of:

[Paul, <[email protected]>, Darren, <[email protected]>, Jennie, <[email protected]>]

Thus, the formatting in the __str__ method isn't working here.

Answer 1

When you print a list, it calls the __str__ for the list, but list internally calls __repr__() for its element. You should implement the __repr__() for your class as well. Example -

class Contacts:
    all_contacts = []

    def __init__(self, name, email):
       self.name = name
       self.email = email
       Contacts.all_contacts.append(self)

    def __str__(self):
       return '%s, <%s>' % (self.name, self.email)

    def __repr__(self):
        return str(self)

Demo -

class Contacts:
    all_contacts = []

    def __init__(self, name, email):
       self.name = name
       self.email = email
       Contacts.all_contacts.append(self)

    def __str__(self):
       return '%s, <%s>' % (self.name, self.email)

    def __repr__(self):
        return str(self)

contact1 = Contacts("Grace1", "[email protected]")
contact2 = Contacts("Grace2", "[email protected]")
contact3 = Contacts("Grace3", "[email protected]")
print(Contacts.all_contacts)

Result -

[Grace1, <[email protected]>, Grace2, <[email protected]>, Grace3, <[email protected]>]

Also, from the output it would seem like the list actually has 6 elements, so you should consider changing that the __repr__ returns.

Answer 2

Your code constructs a list of objects when it says:

Contacts.all_contacts.append(self)

because self is an object, and gets appended to the all_contacts list..

If you want something different, append something different to the all_contacts list.