A simple implementation of priority queue using linear array

Author: codingEzio

chap09_heaps/priority_queue_based_on_linear_array.py

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+# Ref: https://github.com/keon/algorithms/blob/master/algorithms/queues/priority_queue.py
+
+import itertools
+
+
+class PriorityQueueNode:
+    def __init__(self, data, priority):
+        self.data = data
+        self.priority = priority
+
+    def __repr__(self):
+        return f"{self.data}: {self.priority}"
+
+
+class PriorityQueue:
+    """An implementation of priority queue using linear array.
+    """
+
+    def __init__(self, items=None, priorities=None):
+        self.priority_queue_list = []
+
+        if items is None:
+            return None
+        if priorities is None:
+            priorities = itertools.repeat(None)
+
+        for item, priority in zip(items, priorities):
+            self.push(item, priority=priority)
+
+    def __repr__(self):
+        return f"PriorityQueue<{repr(self.priority_queue_list)}>"
+
+    def size(self):
+        return len(self.priority_queue_list)
+
+    def push(self, item, priority=None):
+        """
+        Push the item into the priority queue.
+
+        If priority is not given, priority is set to the value of item.
+        Then the comparison will kinda be like 'John < Alisa' (not accurate!).
+        """
+        priority = item if priority is None else priority
+        pq_node = PriorityQueueNode(item, priority)
+
+        for idx, current in enumerate(self.priority_queue_list):
+            if current.priority < pq_node.priority:
+                self.priority_queue_list.insert(idx, pq_node)
+
+                return None
+
+        self.priority_queue_list.append(pq_node)
+
+    def pop(self):
+        """Remove and return the item with the lowest priority.
+        """
+        return self.priority_queue_list.pop().data
+
+
+def main() -> None:
+    items = ["John", "Alisa"]
+    priorities = [29, 20]
+
+    pq = PriorityQueue(items=items, priorities=priorities)
+
+    pq.push(item="Bobby", priority=23)
+
+    assert str(pq) == "PriorityQueue<[John: 29, Bobby: 23, Alisa: 20]>"
+    assert pq.size() == 3
+    assert pq.pop() == "Alisa"
+
+
+if "__main__" == __name__:
+    main()