Quick recipes for implementing Stacks, Queues, and Linked Lists in Python.

data_structures.py

# with inspiration from Kojin @ Harvard

class Stack:
    """for creating a LIFO data structure"""
    def __init__(self):
        self.items = []

    def size(self):
        return len(self.items)

    def is_empty(self):
        return self.size() == 0

    def push(self, item):
        return self.items.append(item)

    def pop(self):
        if self.is_empty():
            return None
        else:
            return self.items.pop()

    def peek(self):
        if self.is_empty():
            return None
        else:
            return self.items[-1]


class Queue:
    """for creating a FIFO data structure"""
    def __init__(self):
        self.items = []

    def size(self):
        return len(self.items)

    def is_empty(self):
        return self.size() == 0

    def enqueue(self, item):
        return self.items.insert(0, item)

    def dequeue(self):
        if self.is_empty():
            return None
        else:
            return self.items.pop()


class Node:
    """for creating and traversing nodes in a Linked List"""
    def __init__(self, val):
        self.val = val
        self.next = None

    def traverse(self):
        node = self
        while node != None:
            print(node.val)
            node = node.next