#### Double Hash

p
```#!/usr/bin/env python3
"""
Double hashing is a collision resolving technique in Open Addressed Hash tables.
Double hashing uses the idea of applying a second hash function to key when a collision
occurs. The advantage of Double hashing is that it is one of the best form of  probing,
producing a uniform distribution of records throughout a hash table. This technique
does not yield any clusters. It is one of effective method for resolving collisions.

Double hashing can be done using: (hash1(key) + i * hash2(key)) % TABLE_SIZE
Where hash1() and hash2() are hash functions and TABLE_SIZE is size of hash table.

Reference: https://en.wikipedia.org/wiki/Double_hashing
"""
from .hash_table import HashTable
from .number_theory.prime_numbers import is_prime, next_prime

class DoubleHash(HashTable):
"""
Hash Table example with open addressing and Double Hash
"""

def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)

def __hash_function_2(self, value, data):
next_prime_gt = (
next_prime(value % self.size_table)
if not is_prime(value % self.size_table)
else value % self.size_table
)  # gt = bigger than
return next_prime_gt - (data % next_prime_gt)

def __hash_double_function(self, key, data, increment):
return (increment * self.__hash_function_2(key, data)) % self.size_table

def _collision_resolution(self, key, data=None):
"""
Examples:

1. Try to add three data elements when the size is three
>>> dh = DoubleHash(3)
>>> dh.insert_data(10)
>>> dh.insert_data(20)
>>> dh.insert_data(30)
>>> dh.keys()
{1: 10, 2: 20, 0: 30}

2. Try to add three data elements when the size is two
>>> dh = DoubleHash(2)
>>> dh.insert_data(10)
>>> dh.insert_data(20)
>>> dh.insert_data(30)
>>> dh.keys()
{10: 10, 9: 20, 8: 30}

3. Try to add three data elements when the size is four
>>> dh = DoubleHash(4)
>>> dh.insert_data(10)
>>> dh.insert_data(20)
>>> dh.insert_data(30)
>>> dh.keys()
{9: 20, 10: 10, 8: 30}
"""
i = 1
new_key = self.hash_function(data)

while self.values[new_key] is not None and self.values[new_key] != key:
new_key = (
self.__hash_double_function(key, data, i)
if self.balanced_factor() >= self.lim_charge
else None
)
if new_key is None:
break
else:
i += 1

return new_key

if __name__ == "__main__":
import doctest

doctest.testmod()
```  