Using Python to implement stacks and queues

1. Use Python to implement the stack:

1 classstack ():2     def __init__(self):3Self.stack = []4     defEmpty (self):5         returnself.stack==[]6     defpush (Self,data):7 self.stack.append (data)8     defpop (self):9         ifself.empty ():Ten             returnNone; One         Else: A             returnSelf.stack.pop (-1) -     defTop (self): -         ifself.empty (): the             returnNone -         Else: -             returnSelf.stack[-1] -     defLength (self): +         returnLen (Self.stack)

2. Use Python to implement the queue:

classqueue ():def __init__(self): Self.queue= []    defEmpty (self):returnSelf.queue = = []    defEnqueue (self,data): self.queue.append (data)defdequeue (self):ifself.empty ():returnNoneElse:            returnself.queue.pop (0)#return header information and queue length can not be implemented    defHead (self):ifself.empty ():returnNoneElse:            returnSelf.queue[0]defLength (self):returnLen (Self.queue)

Using Python to implement stacks and queues