A very crude, inefficient HashMap implementation.

hashmap.py

#! /usr/bin/env python3

import random

class HashMap:
    def __init__(self, num_buckets=100):
        self.num_buckets = num_buckets
        self.buckets = [[] for _ in range(num_buckets)]
        
    def put(self, key, val):
        index = self._hash(key)

        if len(self.buckets[index]) != 0:
            self.buckets[index].append((key, val))
        else:
            self.buckets[index] = [(key, val)]

    def get(self, key):
        index = self._hash(key)
        if len(self.buckets[index]) == 0:
            raise KeyError(f"KeyError: {key} not found.")
        else:
            for k, val in self.buckets[index]:
                if k == key:
                    return val
            raise KeyError(f"KeyError: {key} not found.")

    def _hash(self, key):
        return key % self.num_buckets

    def __repr__(self):
        return f"{self.buckets}"


if __name__ == "__main__":
    h = HashMap()

    random.seed(42)

    for _ in range(1000):
        key, value = random.randint(1, 1000), random.randint(1, 1000)
        h.put(key, value)

    for _ in range(15):
        key = random.randint(1, 1000)
        try:
            h.get(key)
        except KeyError as e:
            print(e)