'Queue' object has no attribute 'size'

4
votes

I have seen other examples of this happening on StackOverflow, but I didn't understand any of the answers (I'm still a new programmer,) nor did the other examples I saw look quite like mine, else I wouldn't post this question.

I'm running Python 3.2 on Windows 7.

I have never had this happen to me before and I've done classes this way many times, so I don't really know what is different this time. The only difference is that I didn't make all of the Class file; I was given a template to fill in and a test file to try it on. It worked on the test file, but is not working on my file. I have been calling on the methods in the class in the exact same way as the test file (e.g. Lineup.size())

This is my Class:

class Queue:

    # Constructor, which creates a new empty queue:
    def __init__(self):
        self.__items = []

    # Adds a new item to the back of the queue, and returns nothing:
    def queue(self, item):
        self.__items.insert(0,item)
        return

    # Removes and returns the front-most item in the queue.  
    # Returns nothing if the queue is empty.
    def dequeue(self):
        if len(self.__items) == 0:
            return None
        else:
            return self.__items.pop()

    # Returns the front-most item in the queue, and DOES NOT change the queue.  
    def peek(self):
        if len(self.__items) == 0:
            return None
        else:
            return self.__items[(len(self.__items)-1)]

    # Returns True if the queue is empty, and False otherwise:
    def is_empty(self):
        return len(self.__items) == 0

    # Returns the number of items in the queue:
    def size(self):
        return len(self.__items)

    # Removes all items from the queue, and sets the size to 0:
    def clear(self):
        del self.__items[0:len(self.__items)]
        return

    # Returns a string representation of the queue:
    def __str__(self):
        return "".join(str(i) for i in self.__items)

This is my program:

from queue import Queue

Lineup = Queue()

while True:
  decision = str(input("Add, Serve, or Exit: ")).lower()
  if decision == "add":
    if Lineup.size() == 3:
      print("There cannot be more than three people in line.")
      continue
    else:
      person = str(input("Enter the name of the person to add: "))
      Lineup.queue(person)
      continue
  elif decision == "serve":
    if Lineup.is_empty() == True:
      print("The lineup is already empty.")
      continue
    else:
      print("%s has been served."%Lineup.peek())
      Lineup.dequeue()
      continue
  elif (decision == "exit") or (decision == "quit"):
    break
  else:
    print("%s is not a valid command.")
    continue

And this is my error message when I enter "add" as my decision variable:

line 8, in builtins.AttributeError: 'Queue' object has no attribute 'size'

So, what is going on here? What is different about this one?

2
pythonclasspython-3.xqueueattributeerror
it seems you are importing the builtin queue module rather than your own. Try checking what queue.__file__ is set to. – Wessie
Python 3 already contains a queue module. Rename your queue.py to my_queue.py and your code should work. – Blender
Oh wow... how did I not notice that? haha. Thank you. That fixed it. You should "answer this question" so I can give either of you a thumbs up and a checkmark. – Steven
If you don't want to fall into custom code you can also try from collections import deque which is similar to lists but very efficient, and will get you the job done. – TheSHETTY-Paradise

2 Answers

11
votes

Python 3 already has a queue module (which you might want to take a look at). When you import queue, Python finds that queue.py file before it finds your queue.py.

Rename your queue.py file to my_queue.py, change your import statements to from my_queue import Queue, and your code will work as you intend.

-2
votes

try rename size for other name or implement a counter to the list __items some like

def get_size(self):
    cnt = 0
    for i in self.__items:
        cnt++
    return cnt