AdamGold

    def compare_hash(self, other: object) -> bool:
        """compare keys and hashes with different entry"""
        if not isinstance(other, Entry):
            return NotImplemented
        return self.key == other.key and self.hash == other.hash

AdamGold

    def __getitem__(self, key: str) -> Entry:
        """subscript method - object[key]
        use hashing function to find the index"""
        entry = Entry(key)
        index = entry.hash % self.actual_size
        found = self.entries[index]
        while found and not entry.compare_hash(found):
            index = (index + 1) % self.actual_size
            found = self.entries[index]
        if found == None:

AdamGold

    def __setitem__(self, key: str, value: Any) -> int:
        """allow insertion of items with object[key] = value"""
        entry = Entry(key, value)
        index = entry.hash % self.actual_size
        existing_entry = self.entries[index]
        while existing_entry and not entry.compare_hash(existing_entry):
            # don't overlap existing values
            index = (index + 1) % self.actual_size
            existing_entry = self.entries[index]
        self.entries[index] = entry

AdamGold

    def __init__(self, size=10):
        self.entries = [None for _ in range(size * 2)]
        self.actual_size = size * 2
        self.size = size

AdamGold

class HashTable(object):
    def __init__(self, size):
        """initialise hash table"""

    def __getitem__(self, key: str) -> Entry:
        """subscript method - object[key]
        use hashing function to find the index"""

    def __setitem__(self, key: str, value: Any) -> int:
        """allow insertion of items with object[key] = value"""

AdamGold

class Entry(object):
    def __init__(self, key: str, value=None):
        self.key = key
        self.value = value
        
    @property
    def hash(self) -> int:
        """return entry's hash"""
    
    def __repr__(self):

AdamGold

/* https://github.com/lattera/glibc/blob/895ef79e04a953cac1493863bcae29ad85657ee1/malloc/malloc.c#L1044 */
struct malloc_chunk {

  INTERNAL_SIZE_T      mchunk_prev_size;  /* Size of previous chunk (if free).  */
  INTERNAL_SIZE_T      mchunk_size;       /* Size in bytes, including overhead. */

  struct malloc_chunk* fd;         /* double links -- used only if free. */
  struct malloc_chunk* bk;

  /* Only used for large blocks: pointer to next larger size.  */

AdamGold

In [25]: dis.dis("t[a] += b")                                                                                                                                                                                       
  1           0 LOAD_NAME                0 (t)
              2 LOAD_NAME                1 (a)
              4 DUP_TOP_TWO
              6 BINARY_SUBSCR
              8 LOAD_NAME                2 (b)
             10 INPLACE_ADD --> (value in t[a]) += b --> succeeds because list is mutable
             12 ROT_THREE
             14 STORE_SUBSCR --> Assign t[a] = our list --> Fails, t[a] is immutable.
             16 LOAD_CONST               0 (None)

AdamGold

In [22]: t = (1, 2, [3, 4])                                                                                                                                                                                         
In [23]: t[2] += [30, 40]                                                                                                                                                                                           
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-25-af836a8d44a2> in <module>
----> 1 t[2] += [30, 40]

TypeError: 'tuple' object does not support item assignment

In [24]: t                                                                                                                                                                                                          

AdamGold

In [18]: dict.fromkeys(["key1", "key2", "key3"], "DEFAULT_VALUE")                                                                                                                                            
{'key1': 'DEFAULT_VALUE', 'key2': 'DEFAULT_VALUE', 'key3': 'DEFAULT_VALUE'}