Python实现哈希表（分离链接法）

一、python实现哈希表

只使用list，构建简单的哈希表（字典对象）

 

# 不使用字典构造的分离连接法版哈希表
class HashList():
    """  Simple hash function(seperate list table) by python list  """
    def __init__(self, table_size = 457):
        self.usage = 0             # 已用
        self.table_size = table_size  # max size of hash table
        # initial list table and the count num of table's list 
        self.hash_table = [[] for i in range(self.table_size)]
        self.flags = [0 for i in range(self.table_size)]   # the num of element store in each cell list
    
    def __len__(self):
        return self.usage
    
    def __getitem__(self, key):
        return self.get(key)
        
    def __setitem__(self, key, value):
        return self.insert(key, value)

    def __contain__(self, key):
        if self.get(key) is None:
            return False
        else:
            return True

    def hash(self, key):
        return (key + 27) % self.table_size    # simple hash

    def check(self, key):
    # handle nums(int) and chars
        flag = False  # [], "", 0 == False
        if key is not None:
            if isinstance(key, int) or isinstance(key, str):    
                flag = True
            else:
                print("Can't handle other datatype!")    
        else:
            print("Key is None!")                
        return flag
        
    def get_pos(self, key):
        # 每个函数只做自己该做的事
        pos = 0
        if isinstance(key, int):
            pos = self.hash(key)       # [[], [], ... , [[k1, v1], [k2, v2]], ..., []]
        elif isinstance(key, str):
            pos = self.hash(sum(map(lambda x: ord(x), key)))    
        return pos

    def get(self, key):
        value = None             
        if self.check(key):        
            pos = self.get_pos(key) # 遍历key对应列表
            for i in range(self.flags[pos]):
                if self.hash_table[pos][i][0] == key:
                    # 对应pos的list上存在key   print("\nfinding  key:{}, pos:{}, idx:{}".format(key, pos, i))
                    value = self.hash_table[pos][i][1]
                    break
        return value           # invalid key
            
    def insert(self, key, value):
        # Support key datatype: integer and string
        flag = False
        if self.check(key):            
            if self.__contain__(key):
                print("Key:{} exsit!".format(key))  # 真存在key
            else:
                pos = self.get_pos(key)          # key合法但是不存在
                print("Insert key:{}, value:{}, pos:{}".format(key, value, pos))
                if len(self.hash_table[pos]) == 0:
                    self.usage += 1          # if it's empty key, add usage num
                self.hash_table[pos].append([key, value])   # 需存储键和值（对于id password很危险）
                self.flags[pos] += 1     # num of element on this key
                flag = True        
        return flag

    def clear(self):
        self.usage = 0             # 已用
        self.table_size = table_size  # max size of hash table
        self.flags = [0 for i in range(self.table_size)]        
        self.hash_table = [[] for i in range(self.table_size)]
 

 

def main():
    table = HashList()
    table["shopping"] = "8008208820"
    table["12312qweq"] =  [12312,123]
    table[12312] = [12, 2, 123]
    table.insert("helloworld", 12312)
    table.insert("1888888888", "My brother")
    table.insert("1518089898", "No problem")    
    table.insert([], 12312)  
    table.insert("", 12312)  
    table.insert(None, 12312)  
    
    print()
    table.insert(12312, [12, 2, 123])
    table.insert("hash is hash", 110)
    table["FirePolice"] = 119
    
    print('\n',12312, table.get(12312))
    print("12312qweq", table.get("12312qweq"))
    print("hash is hash", table["hash is hash"])
    print("1888888888", table["1888888888"])
    t = HashList()
    [t.insert(chr(ord('a') + i), i) for i in range(26)]
    
if __name__ == "__main__":
    main()