Added doctest to hash_table.py (#11023)

* Added doctest to hash_table.py

* Update hash_table.py

* Update hash_table.py

* Update hash_table.py

* Update hash_table.py

* Apply suggestions from code review

* Update hash_table.py

---------

Co-authored-by: Christian Clauss <cclauss@me.com>

data_structures/hashing/hash_table.py

@@ -52,6 +52,30 @@ class HashTable:
         )
 
     def hash_function(self, key):
+        """
+        Generates hash for the given key value
+
+        Examples:
+
+        Creating HashTable with size 5
+        >>> ht = HashTable(5)
+        >>> ht.hash_function(10)
+        0
+        >>> ht.hash_function(20)
+        0
+        >>> ht.hash_function(4)
+        4
+        >>> ht.hash_function(18)
+        3
+        >>> ht.hash_function(-18)
+        2
+        >>> ht.hash_function(18.5)
+        3.5
+        >>> ht.hash_function(0)
+        0
+        >>> ht.hash_function(-0)
+        0
+        """
         return key % self.size_table
 
     def _step_by_step(self, step_ord):
@@ -105,10 +129,99 @@ class HashTable:
             i += 1
 
     def _set_value(self, key, data):
+        """
+        _set_value functions allows to update value at a particular hash
+
+        Examples:
+        1. _set_value in HashTable of size 5
+        >>> ht = HashTable(5)
+        >>> ht.insert_data(10)
+        >>> ht.insert_data(20)
+        >>> ht.insert_data(30)
+        >>> ht._set_value(0,15)
+        >>> ht.keys()
+        {0: 15, 1: 20, 2: 30}
+
+        2. _set_value in HashTable of size 2
+        >>> ht = HashTable(2)
+        >>> ht.insert_data(17)
+        >>> ht.insert_data(18)
+        >>> ht.insert_data(99)
+        >>> ht._set_value(3,15)
+        >>> ht.keys()
+        {3: 15, 2: 17, 4: 99}
+
+        3. _set_value in HashTable when hash is not present
+        >>> ht = HashTable(2)
+        >>> ht.insert_data(17)
+        >>> ht.insert_data(18)
+        >>> ht.insert_data(99)
+        >>> ht._set_value(0,15)
+        >>> ht.keys()
+        {3: 18, 2: 17, 4: 99, 0: 15}
+
+        4. _set_value in HashTable when multiple hash are not present
+        >>> ht = HashTable(2)
+        >>> ht.insert_data(17)
+        >>> ht.insert_data(18)
+        >>> ht.insert_data(99)
+        >>> ht._set_value(0,15)
+        >>> ht._set_value(1,20)
+        >>> ht.keys()
+        {3: 18, 2: 17, 4: 99, 0: 15, 1: 20}
+        """
         self.values[key] = data
         self._keys[key] = data
 
     def _collision_resolution(self, key, data=None):
+        """
+        This method is a type of open addressing which is used for handling collision.
+
+        In this implementation the concept of linear probing has been used.
+
+        The hash table is searched sequentially from the original location of the
+        hash, if the new hash/location we get is already occupied we check for the next
+        hash/location.
+
+        references:
+            - https://en.wikipedia.org/wiki/Linear_probing
+
+        Examples:
+        1. The collision will be with keys 18 & 99, so new hash will be created for 99
+        >>> ht = HashTable(3)
+        >>> ht.insert_data(17)
+        >>> ht.insert_data(18)
+        >>> ht.insert_data(99)
+        >>> ht.keys()
+        {2: 17, 0: 18, 1: 99}
+
+        2. The collision will be with keys 17 & 101, so new hash
+        will be created for 101
+        >>> ht = HashTable(4)
+        >>> ht.insert_data(17)
+        >>> ht.insert_data(18)
+        >>> ht.insert_data(99)
+        >>> ht.insert_data(101)
+        >>> ht.keys()
+        {1: 17, 2: 18, 3: 99, 0: 101}
+
+        2. The collision will be with all keys, so new hash will be created for all
+        >>> ht = HashTable(1)
+        >>> ht.insert_data(17)
+        >>> ht.insert_data(18)
+        >>> ht.insert_data(99)
+        >>> ht.keys()
+        {2: 17, 3: 18, 4: 99}
+
+        3. Trying to insert float key in hash
+        >>> ht = HashTable(1)
+        >>> ht.insert_data(17)
+        >>> ht.insert_data(18)
+        >>> ht.insert_data(99.99)
+        Traceback (most recent call last):
+        ...
+        TypeError: list indices must be integers or slices, not float
+        """
         new_key = self.hash_function(key + 1)
 
         while self.values[new_key] is not None and self.values[new_key] != key: