Python Python Python Python Python MD5SHA-1SHA-2NTLMPython hash()Pythonhash().__hash__()

Python

Python Python Python

Python

MD5SHA-1SHA-2NTLM

Python hash()

Pythonhash()

.__hash__().__hash__()

Python hash()

>>> hash(1)1>>> hash(10)10>>> hash(10.00)10>>> hash(10.01)230584300921368586>>> hash(-10.01)-230584300921368586

Pythonhash() 64 Python 3 24

11.01

>>> hash(0.1)230584300921369408>>> hash(230584300921369408)230584300921369408>>> hash(0.1) == hash(230584300921369408)True

number 230584300921369408 number 0.1

Python

>>> hash("Bad Behaviour")7164800052134507161

Python Python 3.3 PYTHONHASHSEED

Python 3.3 DOS Scott Crosby Dan Wallach 2003

DOS DOS Scott Crosby

Python

Python Python

Python TypeError a

>>> hash(["R","e","a","l","P","y","t","h","o","n"])Traceback (most recent call last): File "<stdin>", line 1, in <module>TypeError: unhashable type: 'list'

Python id

>>> class Car():...     velocity = 0...     direction = 0...     damage = 0...>>> first_car = Car()>>> second_car = Car()>>> hash(first_car)274643597>>> hash(second_car)274643604

.__hash__()

Python Python

import pprintclass Hashtable:    def __init__(self, elements):        self.bucket_size = len(elements)        self.buckets = [[] for i in range(self.bucket_size)]        self._assign_buckets(elements)    def _assign_buckets(self, elements):        for key, value in elements:            hashed_value = hash(key)            index = hashed_value % self.bucket_size            self.buckets[index].append((key, value))    def get_value(self, input_key):        hashed_value = hash(input_key)        index = hashed_value % self.bucket_size        bucket = self.buckets[index]        for key, value in bucket:            if key == input_key:                return(value)        return None    def __str__(self):        return pprint.pformat(self.buckets) # here pformat is used to return a printable representation of the objectif __name__ == "__main__":     capitals = [        ('France', 'Paris'),        ('United States', 'Washington D.C.'),        ('Italy', 'Rome'),        ('Canada', 'Ottawa')    ]hashtable = Hashtable(capitals)print(hashtable)print(f"The capital of Italy is {hashtable.get_value('Italy')}")

for 9 10 11 12

PYTHONHASHSEED46

[[('United States', 'Washington D.C.'), ('Canada', 'Ottawa')], [], [], [('France', 'Paris'), ('Italy', 'Rome')]]The capital of Italy is Rome

PYTHONHASHSEED Python Python 3.3

Python

Python

hash()

```python hl_lines=3 class Hashtable: def init (self, elements): self.bucket_size = len(elements) * 2 self.buckets = [[] for i in range(self.bucket_size)] self._assign_buckets

Running this example, I ended up with a better distribution of the input data, but I had however a collision and five unused buckets:```console[[], [], [], [('Canada', 'Ottawa')], [], [], [('United States', 'Washington D.C.'), ('Italy', 'Rome')], [('France', 'Paris')]]The capital of Italy is Rome

_assign_buckets()

    def _assign_buckets(self, elements):        self.buckets = [None] * self.bucket_size        for key, value in elements:            hashed_value = hash(key)            index = hashed_value % self.bucket_size            while self.buckets[index] is not None:                print(f"The key {key} collided with {self.buckets[index]}")                index = (index + 1) % self.bucket_size            self.buckets[index] = ((key, value))

Nonewhile

get_value()

    def get_value(self, input_key):        hashed_value = hash(input_key)        index = hashed_value % self.bucket_size        while self.buckets[index] is not None:            key,value = self.buckets[index]            if key == input_key:                return value            index = (index + 1) % self.bucket_size

get_value()None

Italy ( France) Italy

The key Italy collided with ('France', 'Paris')[None, None, ('Canada', 'Ottawa'), None, ('France', 'Paris'), ('Italy', 'Rome'), None, ('United States', 'Washington D.C.')]The capital of Italy is Rome

Italy ( France) FranceItaly

Python

Python Python

>>> chess_players = {...    "Carlsen": 2863,...    "Caruana": 2835,...    "Ding": 2791,...    "Nepomniachtchi": 2784,...    "Vachier-Lagrave": 2778,... }

chess_players

>>> chess_players["Nepomniachtchi"]2784

Python Key Error

>>> chess_players["Mastromatteo"]Traceback (most recent call last): File "<stdin>", line 1, in <module>KeyError: 'Mastromatteo'

.items()

>>> for (k, v) in chess_players.items():...     print(k,v)... Carlsen 2863Caruana 2835Ding 2791Nepomniachtchi 2784Vachier-Lagrave 2778

Python .keys().values()

>>> chess_players.keys()dict_keys(["Carlsen", "Caruana", "Ding", "Nepomniachtchi", "Vachier-Lagrave"])>>> chess_players.values()dict_values([2863, 2835, 2791, 2784, 2778])

>>> chess_players["Grischuk"] = 2777>>> chess_players{'Carlsen': 2863, 'Caruana': 2835, 'Ding': 2791, 'Nepomniachtchi': 2784, 'Vachier-Lagrave': 2778, 'Grischuk': 2777}

hashable TypeError

>>> my_list = ["Giri", "Mamedyarov"]chess_players[my_list] = 2764Traceback (most recent call last): File "<stdin>", line 1, in <module>TypeError: unhashable type: 'list'

del

>>> del chess_players["Grischuk"]>>> chess_players{'Carlsen': 2863, 'Caruana': 2835, 'Ding': 2791, 'Nepomniachtchi': 2784, 'Vachier-Lagrave': 2778}

Python Pythonic

Python Python

Python Python 3.6 Python 3.6 Python 3.7 Guido

PythonPython240

>>> import sys>>> my_dict = {}>>> sys.getsizeof(my_dict)240

Python240

>>> my_dict["a"] = 100>>> sys.getsizeof(my_dict)240

Python 3.6 8 240 Python

>>> for i in range(20):...     my_dict[i] = 100...     print(f"elements = {i+1} size = {sys.getsizeof(my_dict)}")... elements = 1 size = 240elements = 2 size = 240elements = 3 size = 240elements = 4 size = 240elements = 5 size = 240elements = 6 size = 368elements = 7 size = 368elements = 8 size = 368elements = 9 size = 368elements = 10 size = 368elements = 11 size = 648elements = 12 size = 648elements = 13 size = 648elements = 14 size = 648elements = 15 size = 648elements = 16 size = 648elements = 17 size = 648elements = 18 size = 648elements = 19 size = 648elements = 20 size = 648

Python

>>> keys = list(my_dict.keys())>>> for key in keys:...     del my_dict[key]...>>> my_dict{}>>> sys.getsizeof(my_dict)648

.clear() 72

>>> my_dict.clear()>>> sys.getsizeof(my_dict)72

8

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