---
title: "How to implement a hash table data structure from scratch?"  
description: "How to implement a hash table data structure from scratch?"  
author: "Steilla Mitchel"  
published: 2023-06-13  
updated: 2023-06-16  
canonical: https://www.mindstick.com/forum/158727/how-to-implement-a-hash-table-data-structure-from-scratch  
category: "data structure"  
tags: ["hashtable", "data structure"]  
reading_time: 2 minutes  

---

# How to implement a hash table data structure from scratch?

How to implement a [hash table](https://www.mindstick.com/interview/23440/what-is-hash-table) [data structure](https://www.mindstick.com/blog/11221/simple-way-to-learn-dynamic-data-structure-in-c-language) from scratch?

## Replies

### Reply by Aryan Kumar

Sure. A [hash](https://www.mindstick.com/forum/159584/what-are-the-differences-between-a-hashmap-and-a-hash-table-in-c-sharp) table is a data [structure](https://www.mindstick.com/articles/23258/choose-your-business-structure-wisely) that maps keys to values. The keys are hashed into an array of buckets, and the values are stored in the corresponding bucket. Hash tables are a very efficient data structure for storing and retrieving data, because they can access data in constant time.

Here is an example of how to implement a hash [table data](https://answers.mindstick.com/qa/114525/how-to-delete-rows-with-reference-table-data) structure from scratch in Python:

Python

```plaintext
class HashTable:

    def __init__(self, capacity):
        self.capacity = capacity
        self.table = [None] * capacity

    def hash(self, key):
        return hash(key) % self.capacity

    def insert(self, key, value):
        index = self.hash(key)
        bucket = self.table[index]
        if bucket is None:
            bucket = []
        bucket.append((key, value))
        self.table[index] = bucket

    def get(self, key):
        index = self.hash(key)
        bucket = self.table[index]
        if bucket is None:
            return None
        for k, v in bucket:
            if k == key:
                return v
        return None
```

Here is an explanation of the code:

- The `HashTable` class has two attributes: `capacity` and `table`. The `capacity` attribute is the number of buckets in the hash table, and the `table` attribute is a list of buckets.
- The `hash()` method takes a key as input and returns an integer. The integer is the index of the bucket where the key should be stored.
- The `insert()` method takes a key and value as input and inserts the key-value pair into the hash table. The key is hashed into an index, and the key-value pair is stored in the bucket at that index.
- The `get()` method takes a key as input and returns the value associated with that key. The key is hashed into an index, and the value associated with that key is returned.


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Original Source: https://www.mindstick.com/forum/158727/how-to-implement-a-hash-table-data-structure-from-scratch

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