Circular Queue Python Implementation

I have been trying to make my circular queue work for some time now and just thought I'd ask a question and see if I can get any hints. The problem with my circular queue is that the insert method always returns the value False even when the queue is not full. Here is what I have so far.

class CircularQueue:

    def __init__(self, size):
        """
        -------------------------------------------------------
        Initializes an empty queue. Data is stored in a list.
        -------------------------------------------------------
        Postconditions:
          Initializes an empty queue.
        -------------------------------------------------------
        """
        assert size>=0, "size must be >=0"
        self._values = [None] * size
        self._front = 0
        self._rear = 0
        self._size = size
        self.size = 0

        return 

    def __len__(self):
        """
        -------------------------------------------------------
        Returns the size of the queue.
        Use: n = len( q )
        -------------------------------------------------------
        Postconditions:
          Returns the number of values in the queue.
        -------------------------------------------------------
        """
        return len(self._values())


  def is_full(self):
          value = self._rear - self._size
          if self._values[value]==None:
                 full = False
    else:
        full = True
    return full
    def is_empty(self):
        """
        -------------------------------------------------------
        Determines if the queue is empty.
        Use: b = q.is_empty()
        -------------------------------------------------------
        Postconditions:
          Returns True if the queue is empty, False otherwise.
        -------------------------------------------------------
        """
        if len(self._values) == 0:
            empty = True
        else:
            empty = False
        return empty

    def insert(self, value):
        """
        -------------------------------------------------------
        Inserts a copy of value into the queue.
        Use: q.insert( value )
        -------------------------------------------------------
        Preconditions:
          value - a data element (?)
        Postconditions:
          value is added to the rear of the queue.
        -------------------------------------------------------
        """
        if self.is_full() == True:
            inserted = False
        else:
            inserted = True
            self._values[self._rear] = value
            self._rear = (self._rear + 1)% self._size

        return inserted

    def remove( self ):
        """
        -------------------------------------------------------
        Removes and returns value from the queue.
        Use: v = q.remove()
        -------------------------------------------------------
        Postconditions:
          Returns the value at the front of queue - the value is
          removed from queue. Returns None if queue is empty.
        -------------------------------------------------------
        """
        if self.is_empty() == False:
            value = copy.deepcopy(self._values[self._front])
            self._front = (self._front + 1) % self._size
        else:
            value = None

        return value

    def peek(self):
        """
        -------------------------------------------------------
        Peeks at the front of queue.
        Use: v = q.peek()
        -------------------------------------------------------
        Postconditions:
          Returns a copy of the value at the front of queue -
          the value is not removed from queue. Returns None
          if queue is empty.
        -------------------------------------------------------
        """

        if self.is_empty() == True:
            value = None
        else:
            value = copy.deepcopy(self._values[self._front])

        return value

    def print_i(self):
        """
        -------------------------------------------------------
        Prints the contents of queue from front to rear.
        Use: q.print_i()
        -------------------------------------------------------
        Postconditions:
          Prints each value in queue from front to rear.
          Each value starts on a new line.
        -------------------------------------------------------
        """
        for i in range(len(self._values)):
            print(self._values[i])
        return

I just started to try and test it so this is all I have for my testing module.

from circularqueue import CircularQueue

q = CircularQueue(10)

value = q.insert(1)

print(value)

All I'm trying to do here is see if my insert method will return True because I know for a fact that the queue is not full because that is the very first value that I have tried to enter. Any hints?