python 实现一个hashmap

#! /usr/bin/env python
# -*- coding: utf-8 -*-

"""
@Author:_defined
@Time:  2020/7/9 16:41
@Description:  实现一个hashmap
"""


class LinearMap(object):
    """
    桶，链地址法
    """

    def __init__(self):
        self.items = []

    def add(self, k, v):
        self.items.append((k, v))

    def get(self, key):
        for k, v in self.items:
            if key == k:
                return v
        raise KeyError


class BetterMap(object):
    def __init__(self, size=16):
        self.map = [LinearMap() for _ in range(size)]

    def find_map(self, k):
        index = hash(k) & (len(self.map)-1)
        return self.map[index]

    def add(self, k, v):
        m = self.find_map(k)
        m.add(k, v)

    def get(self, k):
        m = self.find_map(k)
        return m.get(k)


class HashMap(object):
    def __init__(self):
        self.maps = BetterMap()
        self.size = 0
        self.max_size = 1 << 30

    def resize(self):
        if self.max_size < (self.size << 1):
            return 0
        new_maps = BetterMap(self.size << 1)
        for m in self.maps.map:
            for k, v in m.items:
                new_maps.add(k, v)
        self.maps = new_maps
        return 1

    def get(self, k):
        return self.maps.get(k)

    def add(self, k, v):
        if self.size == int(len(self.maps.map)*0.75):
            status = self.resize()
            if not status: raise Exception('Maximum space limit exceeded')
        self.maps.add(k, v)
        self.size += 1


if __name__ == '__main__':
    import string
    hashmap = HashMap()
    for k, v in enumerate(string.ascii_letters):
        hashmap.add(k, v)
    print(hashmap)