PYTHON

hash table in python

// a hash table in python is called a dict and can hold any hashable type as key and everything as value
// you can create one using the literal syntax like {key: value}:
dic = {"a": 1, "b": 2}

hash with python

import hashlib

name = "grepper"
hashed_name = hashlib.sha256(hashed_name.encode('utf-8')).hexdigest())
print(hashed_name)
# result: 82475175ad97f60d1e2c57ef5fd8ae45629d555e1644d6f2a37b69b550a96e95

Hash Table data structure python

"""Hash Table
THIS HASH TABLE ASSUMES THAT YOU ARE PUTTING UNIQUE KEYS WHEN YOU...
...CALL put FUNCTION, 
MAKE AN UPDATE FUNCTION IF YOU ARE PUTTING REPEATED KEYS

Included:
	- hash / rehash (using linear probe)
	- load factor
    - put
	- get

Not included:
	- Get prime/ Check prime
    - Resize
    - Update
    and more...
"""
import fractions
class HashTable:
    def __init__(self, size):
        self._size = size
        self._used = 0
        self._keys = [None]*size
        self._values = [None]*size
        
    def hash_function(self, key):
        return (key % self._size)
    
    def rehash(self, old_key):
        return self.hash_function(old_key + 1) # Linear Probe
    
    def load_factor(self):
        return fractions.Fraction(self._used, self._size)
    
    def full(self):
        return self.load_factor() == 1
    
    def put(self, key, value):
        if self.full():
            return "Full"
        
        # There is empty space
        # Get digest
        digest = self.hash_function(key)
        
        # Resolve collisions
        # Rehash if not empty or key does not exist
        while self._keys[digest] is not None and self._keys[digest] != key:
            digest = self.rehash(digest)
            
        # Don't put if key already exists
        if self._keys[digest] == key:
            return "Exists"
        
        # Finally can put in empty space
        else:
            self._keys[digest] = key
            self._values[digest] = value
            self._used += 1 # update used space counter
            return "Entered"
            
    def get(self, key):
        # Get digest
        digest = self.hash_function(key)
        
        # Within the range of the total space
        for _ in range(self._size):
            if self._keys[digest] != key:
                digest = self.rehash(digest)
            else:
                return self._values[digest]
        
        # Not found
        return "Not found"
        
# Test
from randstr import randstr
from random import randint
def HT_Test(HT):
    print(f">>> HashTable:")
    # Make keys and values
    r = randint(8, 15)
    keys = [randint(10, 100) for _ in range(r)]
    vals = list(randstr(len(keys)))
    print(f"Keys to enter: {keys}",
          f"Vals to enter: {vals}",
          f"Key-value pair: {list(zip(keys, vals))}",   # display one list with key-value pair
          sep = "
", end = "

")
    
    # Initiate Hash Table
    H = HT(len(keys) - 2)
    
    # Put the key-value pair into Hash Table
    print("Put:")
    for i in range(len(keys)):
        key, val = keys[i], vals[i]
        print(f"Key: {key}",
              f"Status: {H.put(key, val)}",
              f"Load factor: {H.load_factor()}", 
              sep = " | ")
    print()
    print(f"Keys entered: {H._keys}",
          f"Values entered: {H._vals}", 
          sep = "
", end = "

")
    
    # Get the values in Hash Table for each corresponding key
    print("Get:")
    for key in keys:
        print(f"Key: {key}",
              f"({H.get(key)})",
              sep = " | ")

hash table python

A hash table is a dictionary in python

has_table = {'key_name': key_value}

hash tables in python

hash table definition