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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"""
return len(self.key)
def __repr__(self):
return f"<Entry hash={self.hash}, key={self.key}, value={self.value}>"
def __str__(self):
return str(self.value)
def __eq__(self, other: object) -> bool:
"""Check equation with other entries, e.g dict['a'] == dict['b']"""
if not isinstance(other, Entry):
return NotImplemented
return self.value == other.value
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
class HashTable(object):
def __init__(self, size=10):
self.entries = [None for _ in range(size * 2)]
self.size = size
self.actual_size = size * 2
self.filled_entries = 0
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:
raise KeyError
# both keys and hashes match
return found
def __setitem__(self, key: str, value: Any) -> int:
"""allow insertion of items with object[key] = value"""
if self.filled_entries == self.size:
# no more room
raise KeyError
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
self.filled_entries += 1
return index
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