Hash Map in Python

Question

I want to implement a HashMap in Python. I want to ask a user for an input. depending on his input I am retrieving some information from the HashMap. If the user enters a k

Answer 1

Python dictionary is a built-in type that supports key-value pairs.

streetno = {"1": "Sachin Tendulkar", "2": "Dravid", "3": "Sehwag", "4": "Laxman", "5": "Kohli"}

as well as using the dict keyword:

streetno = dict({"1": "Sachin Tendulkar", "2": "Dravid"}) 

or:

streetno = {}
streetno["1"] = "Sachin Tendulkar" 

Answer 2

class HashMap:
    def __init__(self):
        self.size = 64
        self.map = [None] * self.size

    def _get_hash(self, key):
        hash = 0

        for char in str(key):
            hash += ord(char)
        return hash % self.size

    def add(self, key, value):
        key_hash = self._get_hash(key)
        key_value = [key, value]

        if self.map[key_hash] is None:
            self.map[key_hash] = list([key_value])
            return True
        else:
            for pair in self.map[key_hash]:
                if pair[0] == key:
                    pair[1] = value
                    return True
                else:
                    self.map[key_hash].append(list([key_value]))
                    return True

    def get(self, key):
        key_hash = self._get_hash(key)
        if self.map[key_hash] is not None:
            for pair in self.map[key_hash]: 
                if pair[0] == key:
                    return pair[1]
        return None

    def delete(self, key):
        key_hash = self._get_hash(key)

        if self.map[key_hash] is None :
            return False
        for i in range(0, len(self.map[key_hash])):
            if self.map[key_hash][i][0] == key:
                self.map[key_hash].pop(i)
                return True

    def print(self):

        print('---Phonebook---')
        for item in self.map:
            if item is not None:
                print(str(item))

h = HashMap()

Answer 3

Hash maps are built-in in Python, they're called dictionaries:

streetno = {}                        #create a dictionary called streetno
streetno["1"] = "Sachin Tendulkar"   #assign value to key "1"

Usage:

"1" in streetno                      #check if key "1" is in streetno
streetno["1"]                        #get the value from key "1"

See the documentation for more information, e.g. built-in methods and so on. They're great, and very common in Python programs (unsurprisingly).