Incomplete Object in Python Tutor?

Question

I have this training exercise where I need to find the problems in this program. I can't find them and python tutor does not allow me to see the object created. It just says incomplete object. The program should create a kind of queue for strings. What is wrong with the code?

class A():
"""Eine Art Warteschlange für Strings"""

    def __init__(self, wait = [], now = ""):
        self.wait = wait
        self.now = now

    def new_string(self, x):
        """Fügt einen String zur Warteschlange hinzu"""
        self.wait.append(str(x))

    def next_string(self):
        """Holt den nächsten String aus der Warteschlange, speichert ihn als aktuellen String"""
        self.now = self.wait[0]
        self.wait.pop(0)

    def top(self):
        """Gibt den aktuellen String zurück"""
        return self.now

    def __str__(self):
        return self.top

Can you share the error and traceback for the error you are getting? — Kshitij Saraogi, Jan 26 '17 at 15:29
At a first glance the only thing I notice that you should write class(object) in order to extends object. Look here: http://stackoverflow.com/questions/15374857/should-all-python-classes-extend-object — al27091, Jan 26 '17 at 15:29
theres no error, the program is just not doing what it should, the now string is always empty — Lauch 30000, Jan 26 '17 at 15:35
@Lauch30000 : How do you call the class? What output do you expect? What output does it give you? — Christian, Jan 26 '17 at 15:37
I'm using python3 for example: a = A() a = a.new_string("examplestring") a.next_string() print(a.top) This should return "examplestring" — Lauch 30000, Jan 26 '17 at 15:41
@Lauch30000 Can you reflect this by editing your question or adding a relevant tag? — Kshitij Saraogi, Jan 26 '17 at 15:42

score 1 · Answer 1 · answered Jan 26 '17 at 15:52

Here are the few bugs I came across in your class.(There may be more):

Under indentation of the class docs.
Fix: Indent it by 4 spaces to the right.
The __str__ magic method doesn't return a string.
Fix: Replace self.top with self.top(). You would want to return the value returned by the method top.
Not updating the attribute now whenever new_string is added.
Since, you are using the object's now attribute in __str__, it is advisable to update it whenever an empty object is initialised using new_string method. There are several ways to do. I would suggest you fix this as you see fit.

Example:

In []: a = A()
In []: a.new_string('foo')
In []: print(a)

In []: a.now
Out[]: ''
In []: a.wait
Out[]: ['foo']

Incomplete Object in Python Tutor?

1 Answers1