Restructured queue.py and stack.py

pydatastructs/miscellaneous_data_structures/queue.py

@@ -1,5 +1,5 @@
 from pydatastructs.linear_data_structures import DynamicOneDimensionalArray, SinglyLinkedList
-from pydatastructs.utils.misc_util import NoneType, LinkedListNode
+from pydatastructs.utils.misc_util import NoneType, LinkedListNode, _check_type
 from copy import deepcopy as dc
 
 __all__ = [
@@ -94,7 +94,7 @@ def append(self, x):
 
     def popleft(self):
         if self.is_empty:
-            raise ValueError("Queue is empty.")
+            raise IndexError("Queue is empty.")
         return_value = dc(self.items[self.front])
         front_temp = self.front
         if self.front == self.rear:
@@ -108,6 +108,7 @@ def popleft(self):
         self.items.delete(front_temp)
         return return_value
 
+
     @property
     def rear(self):
         return self.items._last_pos_filled
@@ -128,7 +129,7 @@ def __str__(self):
 
 class LinkedListQueue(Queue):
 
-    __slots__ = ['front', 'rear', 'size', '_dtype']
+    __slots__ = ['_dtype']
 
     def __new__(cls, items=None, dtype=NoneType):
         obj = object.__new__(cls)
@@ -140,41 +141,40 @@ def __new__(cls, items=None, dtype=NoneType):
             if len(items) != 0 and dtype is NoneType:
                 obj._dtype = type(items[0])
             for x in items:
-                if type(x) == obj._dtype:
-                    obj.queue.append(x)
-                else:
-                    raise TypeError("Expected %s but got %s"%(obj._dtype, type(x)))
+                obj.append(x)
         else:
             raise TypeError("Expected type: list/tuple")
-        obj.front = obj.queue.head
-        obj.rear = obj.queue.tail
-        obj.size = obj.queue.size
         return obj
 
     def append(self, x):
         if self._dtype is NoneType:
             self._dtype = type(x)
-        elif type(x) is not self._dtype:
+        elif not _check_type(x, self._dtype):
             raise TypeError("Expected %s but got %s"%(self._dtype, type(x)))
-        self.size += 1
         self.queue.append(x)
-        if self.front is None:
-            self.front = self.queue.head
-        self.rear = self.queue.tail
 
     def popleft(self):
         if self.is_empty:
-            raise ValueError("Queue is empty.")
-        self.size -= 1
+            raise IndexError("Queue is empty.")
         return_value = self.queue.pop_left()
-        self.front = self.queue.head
-        self.rear = self.queue.tail
         return return_value
 
     @property
     def is_empty(self):
         return self.size == 0
 
+    @property
+    def front(self):
+        return self.queue.head
+
+    @property
+    def rear(self):
+        return self.queue.tail
+
+    @property
+    def size(self):
+        return self.queue.size
+
     def __len__(self):
         return self.size
 

pydatastructs/miscellaneous_data_structures/stack.py

@@ -30,7 +30,7 @@ class Stack(object):
     Examples
     ========
 
-    >>> from pydatastructs import Stack
+    >>> from pydatastructs.miscellaneous_data_structures.stack import Stack
     >>> s = Stack()
     >>> s.push(1)
     >>> s.push(2)
@@ -64,16 +64,16 @@ def pop(self, *args, **kwargs):
 
     @property
     def is_empty(self):
-        return None
+        raise NotImplementedError(
+              "This is an abstract method.")
 
     @property
     def peek(self):
-        return None
+        raise NotImplementedError(
+              "This is an abstract method.")
 
 class ArrayStack(Stack):
 
-    __slots__ = ['items']
-
     def __new__(cls, items=None, dtype=NoneType):
         if items is None:
             items = DynamicOneDimensionalArray(dtype, 0)
@@ -90,7 +90,7 @@ def push(self, x):
 
     def pop(self):
         if self.is_empty:
-            raise ValueError("Stack is empty")
+            raise IndexError("Stack is empty")
 
         top_element = dc(self.items[self.items._last_pos_filled])
         self.items.delete(self.items._last_pos_filled)
@@ -104,6 +104,9 @@ def is_empty(self):
     def peek(self):
         return self.items[self.items._last_pos_filled]
 
+    def __len__(self):
+        return self.items.size
+
     def __str__(self):
         """
         Used for printing.

pydatastructs/miscellaneous_data_structures/tests/test_queue.py

@@ -17,7 +17,7 @@ def test_Queue():
     assert len(q1) == 0
 
     q1 = Queue()
-    raises(ValueError, lambda: q1.popleft())
+    raises(IndexError, lambda: q1.popleft())
 
     q1 = Queue(implementation='linkedlist')
     q1.append(1)
@@ -35,4 +35,4 @@ def test_Queue():
     assert q1.popleft().data == 2
     assert q1.popleft().data == 3
     assert len(q1) == 0
-    raises(ValueError, lambda: q1.popleft())
+    raises(IndexError, lambda: q1.popleft())

pydatastructs/miscellaneous_data_structures/tests/test_stack.py

@@ -14,7 +14,8 @@ def test_Stack():
     assert s.pop() == 2
     assert s.pop() == 1
     assert s.is_empty is True
-    assert raises(ValueError, lambda : s.pop())
+    assert raises(IndexError, lambda : s.pop())
     _s = Stack(items=[1, 2, 3])
     assert str(_s) == '[1, 2, 3]'
+    assert len(_s) == 3
     assert raises(NotImplementedError, lambda: Stack(implementation=''))