Adding queue_from_stack in stacks folder

data_structures/stacks/queue_using_stack.py

@@ -0,0 +1,110 @@
+from .stack import Stack, StackOverflowError
+
+
+class Queue:
+    """
+    A queue is an abstract data type that works on the principle of
+    First In, First Out (FIFO). Its principal operations include enqueue()
+    and dequeue(). enqueue() add an element to the end of the queue while
+    dequeue() removes and element from the front of the queue.
+    https://en.wikipedia.org/wiki/Queue_(abstract_data_type)
+    """
+
+    def __init__(self, limit: int = 10) -> None:
+        self.stack1 = Stack(limit)
+        self.stack2 = Stack(limit)
+        self.limit = limit
+
+    def __bool__(self) -> bool:
+        return bool(self.stack1)
+
+    def __str__(self) -> str:
+        return str(self.stack1)
+
+    def enqueue(self, data: int) -> None:
+        """Add an element to the end of queue."""
+        while not self.stack1.is_empty():
+            self.stack2.push(self.stack1.pop())
+
+        self.stack1.push(data)
+
+        while not self.stack2.is_empty():
+            self.stack1.push(self.stack2.pop())
+
+    def dequeue(self) -> int:
+        """Remove and element from the front of queue."""
+        return self.stack1.pop()
+
+    def front(self) -> int:
+        """Return the value of the element in front of the queue."""
+        return self.stack1.peek()
+
+    def is_empty(self) -> bool:
+        """Check if the queue is empty."""
+        return not bool(self.stack1)
+
+    def is_full(self) -> bool:
+        return self.size() == self.limit
+
+    def size(self) -> int:
+        """Return the size of the queue."""
+        return self.stack1.size()
+
+    def __contains__(self, data: int) -> int:
+        """Check if item is in the queue."""
+        return data in self.stack1
+
+
+def test_queue() -> None:
+    """
+    >>> test_queue()
+    """
+    queue = Queue(10)
+    assert queue.is_empty() is True
+    assert queue.is_full() is False
+    assert bool(queue) is False
+    assert str(queue) == "[]"
+
+    try:
+        queue.dequeue()
+        assert False  # This should not happen
+    except IndexError:
+        assert True  # This should happen
+
+    try:
+        queue.front()
+        assert False  # This should not happen
+    except IndexError:
+        assert True  # This should happen
+
+    for i in range(10):
+        assert queue.size() == i
+        queue.enqueue(i)
+
+    assert queue.is_full() is True
+    assert queue.is_empty() is False
+    assert bool(queue) is True
+    assert str(queue) == str(list(range(10))[::-1])
+    assert queue.dequeue() == 0
+    assert queue.front() == 1
+
+    queue.enqueue(100)
+    assert str(queue) == str([100, 9, 8, 7, 6, 5, 4, 3, 2, 1])
+
+    try:
+        queue.enqueue(0)
+        assert False  # This should not happen
+    except StackOverflowError:
+        assert True  # This should happen
+
+    assert queue.is_empty() is False
+    assert queue.size() == 10
+
+    assert 50 not in queue
+    assert 100 in queue
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()