string - Python: How to set up a __str__ function in a PriorityQueue -

i have made priority queue functions use binary heaps functions. however, in testing file trying print out queue this.

your queue looks this: 15 -> 45 -> 10 -> 100 

somewhere that, keeps printing out queue stored rather items in queue, example of this:

<priorityqueue.priorityqueue object @ 0x01e95530> 

i read on pythondocs , concluded need str function. however, having trouble creating me out here on how like? lot. here whole amount of code.

class heap(object):      def __init__(self, items=none):          '''post: heap created specified items.'''          self.heap = [none]         if items none:             self.heap_size = 0         else:             self.heap += items             self.heap_size = len(items)             self._build_heap()      def size(self):          '''post: returns number of items in heap.'''          return self.heap_size      def _heapify(self, position):          '''pre: items 0 position - 1 satisfy heap property.            post: heap property satisfied entire heap.'''          item = self.heap[position]         while position * 2 <= self.heap_size:             child = position * 2             # if right child, determine maximum of 2 children.             if (child != self.heap_size , self.heap[child+1] > self.heap[child]):                 child += 1             if self.heap[child] > item:                 self.heap[position] = self.heap[child]                 position = child             else:                 break         self.heap[position] = item      def delete_max(self):          '''pre: heap property satisfied            post: maximum element in heap removed , returned. '''          if self.heap_size > 0:             max_item = self.heap[1]             self.heap[1] = self.heap[self.heap_size]             self.heap_size -= 1             self.heap.pop()             if self.heap_size > 0:                 self._heapify(1)             return max_item      def insert(self, item):          '''pre: heap property satisfied.            post: item inserted in proper location in heap.'''          self.heap_size += 1         # extend length of list.         self.heap.append(none)         position = self.heap_size         parent = position // 2         while parent > 0 , self.heap[parent] < item:             # move item down.             self.heap[position] = self.heap[parent]             position = parent             parent = position // 2         # puts new item in correct spot.         self.heap[position] = item      def _build_heap(self):          ''' pre: self.heap has values in 1 self.heap_size            post: heap property satisfied entire heap. '''          # 1 through self.heap_size.          in range(self.heap_size // 2, 0, -1): # stops @ 1.             self._heapify(i)      def heapsort(self):          '''pre: heap property satisfied.            post: items sorted in self.heap[1:self.sorted_size].'''          sorted_size = self.heap_size          in range(0, sorted_size -1):             # since delete_max calls pop remove item, need append dummy value avoid illegal index.             self.heap.append(none)             item = self.delete_max()             self.heap[sorted_size - i] = item 

above heap class priorityqueue takes from: below pq class , test file.

#priorityqueue.py myheap import heap   class priorityqueue(object):      def __init__(self):         self.heap = heap()      def enqueue(self, priority, item):         '''post: item inserted specified priority in pq.'''         self.heap.insert((priority, item))         return item      def first(self):         '''post: returns not remove highest priority item pq.'''         return self.heap.size()       def dequeue(self):         '''post: removes , returns highest priority item pq.'''         if self.heap.size() none:             raise valueerror("error queue empty.")         x = self.first()         self.heap.delete_max()         return x      def size(self):         '''post: returns number of items in pq.'''         return self.heap.size() 

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from priorityqueue import priorityqueue  pq = priorityqueue()   print(pq.enqueue(1, 10)) print(pq.enqueue(2, 5)) print(pq.enqueue(3, 90)) print pq print(pq.size()) 

edit: tried following:

 def __str__(self):         return str(self.heap) 

this prints out this:

<myheap.heap object @ 0x01e255f0> 

ok, idea of __str__ return sort of string represents object in human-readable way. have construct string , whatever return printed instead of

<priorityqueue.priorityqueue object @ 0x01e95530> 

in case, have return items of self.heap.heap, separated ->. work output described:

def __str__(self):     if self.size():         heap_items = [str(i) in self.heap.heap if i]         heap_items_str = ' -> '.join(heap_items)         return "your queue looks this: {}".format(heap_items_str)     else:         return "your queue empty." 

note we're using self.heap.heap, not self.heap because self in case priorityqueue instance, , priorityqueue has .heap property contains heap. it's heap want call .heap on, in-turn gives list we're going for.