class Array(object):
  def __init__(self, size = 32, init = None):
    self._size = size
    self._items = [init] * size
  def __getitem__(self, index):
    return self._items[index]
  def __setitem__(self, index, value):
    self._items[index] = value
  def __len__(self):
    return self._size
  def clear(self, value = None):
    for i in range(self,_items):
      self._items[i] = value
  def __iter__(self):
    for item in self._items:
      yield item
class Slot(object):
  """
  定義一個(gè)哈希表數(shù)組的槽
  注意：一個(gè)槽有三種狀態(tài)
  1. 從未被使用過(guò)，HashMap.UNUSED。 此槽沒(méi)有被使用和沖突過(guò)，查找時(shí)只要找到UNUSED 就不用再繼續(xù)探查了
  2. 使用過(guò)但是remove了， 此時(shí)是HashMap.EMPTY，該談差點(diǎn)后面的元素仍可能是有key
  3. 槽正在使用Slot 節(jié)點(diǎn)
  """
  def __init__(self, key, value):
    self.key = key
    self.value = value
class HashTable(object):
  UNUSED = None # 表示slot 沒(méi)有被使用過(guò)
  EMPTY = Slot(None, None) # 使用過(guò)被刪除
  def __init__(self):
    self._table = Array(8, init = HashTable.UNUSED) # 初始化，數(shù)組的每個(gè)元素都是UNUSED
    self.length = 0
  @property # 內(nèi)置裝飾器，把方法變成屬性
  def _load_factor(self):
    return self.length/float(len(self._table))
  def __len__(self):
    return self.length
  def _hash(self, key):
    return abs(hash(key)) % len(self._table) # abs函數(shù)返回絕對(duì)值 hash 是內(nèi)置函數(shù) _hash 直接使用內(nèi)置的哈希函數(shù)，對(duì)數(shù)組的長(zhǎng)度取模
  def _find_key(self, key):
    index = self._hash(key) # 先用 _hash方法計(jì)算出槽的位置
    _len = len(self._table) # 現(xiàn)保存下來(lái)長(zhǎng)度
    while self._table[index] is not HashTable.UNUSED:  # 如果這個(gè)槽不是沒(méi)有被使用過(guò)
      if self._table[index] is HashTable.EMPTY: # 如果這個(gè)槽是，曾經(jīng)有過(guò)值，不過(guò)被刪除了
        index = (index*5 +1 ) % _len    # cpython 使用的一種解決哈希沖突的方式
        continue
      elif self._table[index].key == key: # 正在使用， 如果key值相同
        return index
      else: # 這里就只剩最后一種可能， 正在使用，但是key沒(méi)有找到
        index = (index *5 +1) % _len
    return None
  def _slot_can_insert(self, index): # 判斷一個(gè)槽是否可以插入
    return (self._table[index] is HashTable.EMPTY or self._table[index] is HashTable.UNUSED)
  def _find_slot_for_insert(self,key):  # 尋找一個(gè)空槽，用來(lái)插入
    index = self._hash(key)
    _len = len(self._table)
    while not self._slot_can_insert(index):
      index = (index*5 + 1) % _len
    return index
  def __contains__(self, key):   # 實(shí)現(xiàn)一個(gè)in操作符
    index = self._find_key(key)
    return index is not None
  def add(self, key, value):
    if key in self:  # 上面實(shí)現(xiàn)的in操作符
      index = self._find_key(key)
      self._table[index].value = value
      return False  # 返回False 表示沒(méi)有執(zhí)行插入操作，執(zhí)行的是更新操作
    else:
      index = self._find_slot_for_insert(key)
      self._table[index] = Slot(key, value) # 這兩部可能會(huì)調(diào)用_slot_can_insert 函數(shù)，不管是哪種情況，EMPTY 或 是 UNUSEZD，都將這個(gè)節(jié)點(diǎn)聲明為Slot類
      self.length += 1
      if self._load_factor >= 0.8:
        self._rehash()   # 當(dāng)空間占用大于0.8 的時(shí)候，進(jìn)行rehash 重新分配空間。
      return True
  def _rehash(self):
    old_table = self._table
    newsize = len(self._table) *2
    self._table = Array(newsize, HashTable.UNUSED)
    self.length = 0
    for slot in old_table:
      if slot is not HashTable.UNUSED and slot is not HashTable.EMPTY:  # 判斷這個(gè)slot 是有值的
        index = self._find_slot_for_insert(slot.key)  # 找到一個(gè)可以插入的槽
        self._table[index] = slot
        self.length += 1
  def get(self, key, default = None):
    index = self._find_key(key)
    if index is None:
      return default
    else:
      return self._table[index].value
  def remove(self,key):
    index = self._find_key(key)
    if index is None:
      raise KeyError()
    value = self._table[index].value
    self.length -= 1
    self._table[index] = HashTable.EMPTY
    return value
  def __iter__(self):   # 遍歷操作，python 字典默認(rèn)遍歷的是key，這里實(shí)現(xiàn)的也是遍歷key
    for slot in self._table:
      if slot not in(HashTable.EMPTY, HashTable.UNUSED):
        yield slot.key
class DictADT(HashTable):

  def __setitem__(self, key, value):  # 設(shè)定給定鍵的值
    self.add(key, value)
  def __getitem__(self, key):   # 返回給定鍵的值
    if key not in self:
      raise KeyError()
    else:
      return self.get(key)
  def _iter_slot(self):
    for slot in self._table:
      if slot not in (HashTable.EMPTY, HashTable.UNUSED):
        yield slot
  def items(self):
    for slot in self._iter_slot():
      yield (slot.key, slot.value)
  def keys(self):
    for slot in self._iter_slot():
      yield slot.key
  def values(self):
    for slot in self._iter_slot():
      yield slot.value
def test_dict():
  import random
  d = DictADT()
  d['a'] = 1   # 這時(shí)候調(diào)用 __setitem__ 方法
  assert d['a'] == 1
  d.remove('a')
  l = list(range(30))
  random.suffle(l)  # 打亂l
  for i in l:
    d.add(i, i )
  for i in range(30):
    assert d.get(i) == i
  assert sorted (list(d.keys())) == sorted(l)