Simple hash table implementation

hash_table.py

class HashTable(object):
    def __init__(self):
        self.table = [None]*10000

    def store(self, string):
        hash_code = self.calculate_hash_value(string)
        bucket = [] if not self.table[hash_code] else self.table[hash_code]
        bucket.append(string)
        self.table[hash_code] = bucket

    def lookup(self, string):
        hash_code = self.calculate_hash_value(string)
        bucket = self.table[hash_code]
        if bucket != None:
            if string in bucket: return hash_code
        return -1

    def calculate_hash_value(self, string):
        #Only use first 2 chars to calc hash code
        return (ord(string[0])*100) + ord(string[1])