hash_table.py

import random

def hash_mod(key, mod, func=hash):
    return func(key) % mod

def hash_table(m):
    # initial hash table, m empty entries
    return [[] for i in range(m)]

def contained(key, list_of_items):
    """ checks if key is in list_of_items
        returns location in list (if found), or None"""
    for k in range(len(list_of_items)):
        if key == list_of_items[k][0]:
            return k  # return index of candidate in list 
    return None

def find(key, table, func=hash):
    """ finds an item in a hash table and returns it.
        If the item is not found, returns None"""
    mod = len(table)
    i = hash_mod(key, mod, func)    
    list_of_items = table[i]
    k = contained(key, list_of_items)
    if k != None:  # key exists in table
        return list_of_items[k][1]
    return None
        
def insert(key, value, table, func=hash):
    """ inserts an item into a hash table. If key already
        exists, the value is updated. Always returns None"""
    mod = len(table)
    i = hash_mod(key, mod, func)
    list_of_items = table[i]
    k = contained(key, list_of_items)
    if k != None:  # key exists in table
        list_of_items[k] = (key, value)
    else:
        list_of_items.append((key, value))
    return None

def delete(key, table, func=hash):
    """ deletes an item from a hash table. """
    raise NotImplemented