Timer class to measure elapsed time

timer.py

import time
import pickle
from collections import defaultdict


class Timer:

    def __init__(self):
        self.time_pool = defaultdict(list)
        self.start_dict = {}

    def start(self, key='_default'):
        self.start_dict[key] = time.time()

    def stop(self, key='_default'):
        if key not in self.start_dict.keys():
            errmsg = 'Timer has not started yet. key:{}'.format(key)
            raise ValueError(errmsg)
        elapsed = time.time() - self.start_dict[key]
        self.time_pool[key].append(elapsed)

    def get_all(self):
        return dict(self.time_pool)

    def get(self, key='_default'):
        return self.time_pool[key]

    def save_pickle(self, save_path):
        with open(save_path, 'wb') as f:
                pickle.dump(dict(self.time_pool), f)