python 实现计时器

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方式一：建立一个类

代码

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import time

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

    def start(self):
        if self._start is not None:
            raise RuntimeError('Already started')
        self._start = self._func()

    def stop(self):
        if self._start is None:
            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, *args):
        self.stop()


def timer(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        start = time.perf_counter()
        func(*args, **kwargs)
        end = time.perf_counter()
        print('{}.{} : {}'.format(func.__module__, func.__name__, end - start))
    return wrapper

演示

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from timer import Timer


def countdown(n):
    while n > 0:
        n -= 1


# Use 1: Explicit start/stop
t = Timer()
t.start()
countdown(1000000)
t.stop()
print(t.elapsed) # 0.0429959

# Use 2: As a context manager
with Timer() as t:
    countdown(1000000)
print(t.elapsed) # 0.0440638

方式二：装饰器

代码

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import time
from functools import wraps

def timer(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        start = time.perf_counter()
        func(*args, **kwargs)
        end = time.perf_counter()
        print('{}.{} : {}'.format(func.__module__, func.__name__, end - start))
    return wrapper

演示

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from timer import timer

@timer
def countdown(n):
    while n > 0:
        n -= 1


countdown(1000000) # __main__.countdown : 0.0442

注意事项

  • time.perf_counter() 记录的是钟表时间，包含了所有休眠时间
  • time.process_time() 只计算该进程所花费的CPU时间
  • 单位是秒