else

Stack data structure

Stack/README.md

@@ -0,0 +1,35 @@
+Stack
+======
+
+A class to imitate the [Stack](http://en.wikipedia.org/wiki/Stack_(abstract_data_type)) data structure.
+
+
+    class Stack:
+    	Class to replicate a Stack data structure.
+    	Attributes: maxlen, name
+    	Methods: pop, populate, push, top, truncate
+    
+    	def deepcopy(self):
+    		Return a deep copy of this Stack as a new object
+    
+    	def pop(self, count=1):
+    		Pop the last `count` items off of the Stack. Default 1
+    		returns the most recently popped item
+    
+    	def populate(self, itemlist, destructive=False):
+    		Push as many items as possible from `itemlist` onto the Stack
+    		if `destructive`==True, the current data will be overwritten
+    		and discard the rest.
+    
+    	def push(self, item):
+    		Push an item onto the end of the Stack
+    
+    
+    	def top(self):
+    		Return the item on the top of the stack without popping it
+    
+    	def truncate(self, value):
+    		Remove all items from the Stack after index `value`, and set
+    		`maxlen` to `value`, preventing the addition of further items.
+    		returns None
+    

Stack/stack.py

@@ -0,0 +1,119 @@
+import copy
+class StackError(Exception):
+	pass
+
+
+class Stack:
+	"""
+	Class to replicate a Stack data structure.
+	Attributes: maxlen, name
+	Methods: pop, populate, push, top, truncate
+	"""
+	def __init__(self, maxlen=None, name=""):
+		self.maxlen = maxlen
+		self.name = str(name)
+		self.data = []
+
+	def __get__(self):
+		return self.data
+
+	def __len__(self):
+		return len(self.data)
+
+	def __getitem__(self, index):
+		return self.data[index]
+
+	def __setattr__(self, key, value):
+		if key == "name":
+			value = str(value)
+		if key == "maxlen" and value is not None:
+			if value < 0:
+				raise StackError()
+			if len(self) > value:
+				sizediff = len(self) - value
+				sizediff = str(sizediff)
+				e = ("Cannot set `maxlen` below current `len` or %s items "
+				"would be lost. Try Stack.pop(%s) or Stack.truncate(%d)")
+				raise StackError(e % (sizediff, sizediff, value))
+		if key == "data" and self.maxlen is not None:
+			if len(value) > self.maxlen:
+				raise StackError("List is longer than `maxlen` (%d/%d)" %
+					(len(value), self.maxlen))
+		super(Stack, self).__setattr__(key, value)
+
+	def __repr__(self):
+		display = self.name
+		display += "[|"
+		display += ', '.join([item.__repr__() for item in self.data])
+		display += "|]"
+		if self.maxlen is not None:
+			display += str(self.maxlen - len(self))
+		return display
+
+	def deepcopy(self):
+		"""
+		Return a deep copy of this Stack as a new object
+		"""
+		copystack = Stack(self.maxlen, self.name)
+		copystack.populate(copy.deepcopy(self.data))
+		return copystack
+
+	def pop(self, count=1):
+		"""
+		Pop the last `count` items off of the Stack. Default 1
+		returns the most recently popped item
+		"""
+		for c in range(count):
+			if len(self) == 0:
+				raise StackError("Cannot pop from empty Stack")
+			lastitem = self.data[-1]
+			self.data = self.data[:-1]
+		return lastitem
+
+	def populate(self, itemlist, destructive=False):
+		"""
+		Push as many items as possible from `itemlist` onto the Stack
+		if `destructive`==True, the current data will be overwritten
+		and discard the rest.
+		"""
+		if isinstance(itemlist, range):
+			itemlist = list(itemlist)
+		if isinstance(itemlist, list):
+			if destructive:
+				itemlist = itemlist[:self.maxlen]
+				self.data = itemlist
+			else:
+				if self.maxlen:
+					itemlist = itemlist[:self.maxlen - len(self)]
+				self.data += itemlist
+		else:
+			raise StackError("Stack.populate only accepts list or range type")
+
+	def push(self, item):
+		"""
+		Push an item onto the end of the Stack
+		"""
+		if item is self:
+			raise StackError("Cannot push Stack onto itself")
+		if self.maxlen is None or len(self) < self.maxlen:
+			self.data.append(item)
+		else:
+			raise StackError("Cannot push item onto full Stack")
+
+	def top(self):
+		"""
+		Return the item on the top of the stack without popping it
+		"""
+		if len(self) > 0:
+			return self.data[-1]
+		else:
+			raise StackError("Stack is empty")
+
+	def truncate(self, value):
+		"""
+		Remove all items from the Stack after index `value`, and set
+		`maxlen` to `value`, preventing the addition of further items.
+		returns None
+		"""
+		self.data = self.data[:value]
+		self.maxlen = value