# coding=utf-8
import math
import time


class Timer:
    '''
    計算程式執行時間
    t = Timer()
    with t:
        執行檢測的程式
    print t.elapsed
    '''

    def __init__(self, func=time.perf_counter):
        self.elapsed = 0.0
        self._func = func
        self._start = None

    def start(self):
        if self._start:
            raise RuntimeError('Already started!')
        self._start = self._func()

    def stop(self):
        if not self._start:
            raise RuntimeError('Not started')
        end = self._func()
        self.elapsed += end - self._start
        self._start = None

    def reset(self):
        self.elapsed = 0.0

    @property
    def running(self):
        return self._start is not None

    def __enter__(self):
        self.start()
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.stop()


def create(num):
    result = []
    result_append = result.append
    sqrt = math.sqrt
    for i in range(num):
        result_append(sqrt(i))


if __name__ == '__main__':
    t = Timer()
    with t:
        print('執行狀況：{0}'.format(t.running))
        create(10000000)
    print(t.elapsed)
    print('執行狀況：{0}'.format(t.running))