Python stack and queue classes, implemented using lists
There are a few things to mention.

At first, it might be a good idea to initialize both Queue and Stack with empty lists by default:

def __init__(self, queue=None):
    self.queue = queue or []    # if queue is given, it overrides the default


Next, it doesn't make sense to write something like if len(self.queue)!=0 since it is equivalent to if self.queue (empty list is False when it's casted to bool). You can go even further and introduce the property called size using the built-in decorator:

@property
def size(self):
    return len(self.queue)


Now it can be accessed by self.size without a function call.