What Would Python Display?

In this section, you need to think about what python would display if the code below were input to a python interpreter.

Read over the Link class in lab07.py. Make sure you understand the doctests.

To check the correctness of your answer, you can start a python interpreter, input the code into it, and compare the output displayed in the terminal with yours. It is ok for the interpreter to output nothing or raise an error.

Use Ok to test your knowledge with the following "What Would Python Display?" questions:

python ok -q wwpd -u

Important: Enter Error if you believe a error occurs.

class A:
    def __init__(self, x):
        self.x = x

    def __repr__(self):
         return self.x

    def __str__(self):
         return self.x * 2

class B:
    def __init__(self):
         print('boo!')
         self.a = []

    def add_a(self, a):
         self.a.append(a)

    def __repr__(self):
         print(len(self.a))
         ret = ''
         for a in self.a:
             ret += str(a)
         return ret

>>> A('one')
______

>>> print(A('one'))
______

>>> repr(A('two'))
______

>>> b = B()
______

>>> b.add_a(A('a'))
>>> b.add_a(A('b'))
>>> b
______

>>> link = Link(1000)
>>> link.first
______

>>> link.rest is Link.empty
______

>>> link = Link(1000, 2000)
______

>>> link = Link(1000, Link())
______

>>> link = Link(1, Link(2, Link(3)))
>>> link.first
______

>>> link.rest.first
______

>>> link.rest.rest.rest is Link.empty
______

>>> link.first = 9001
>>> link.first
______

>>> link.rest = link.rest.rest
>>> link.rest.first
______

>>> link = Link(1)
>>> link.rest = link
>>> link.rest.rest.rest.rest.first
______

>>> link = Link(2, Link(3, Link(4)))
>>> link2 = Link(1, link)
>>> link2.first
______

>>> link2.rest.first
______

>>> link = Link(5, Link(6, Link(7)))
>>> link                  # Look at the __repr__ method of Link
______

>>> print(link)          # Look at the __str__ method of Link
______