Question

我正在为dkfileutils编写Path.touch测试：

class Path(str):
    def touch(self, mode=0o666, exist_ok=True):
        """Create this file with the given access mode, if it doesn't exist.
           (based on https://github.com/python/cpython/blob/master/Lib/pathlib.py)
        """
        if exist_ok:
            # First try to bump modification time
            # Implementation note: GNU touch uses the UTIME_NOW option of
            # the utimensat() / futimens() functions.
            try:
                os.utime(self, None)
            except OSError:
                # Avoid exception chaining
                pass
            else:
                return
        flags = os.O_CREAT | os.O_WRONLY
        if not exist_ok:
            flags |= os.O_EXCL
        fd = os.open(self, flags, mode)
        os.close(fd)

我尝试了以下各种变体..

def test_touch():
    before = time.time()
    with open('a', 'w') as fp:
        fp.write('a')
    after = time.time()

    assert before <= after

    a = Path('a')
    a_before_touch = a.getmtime()
    assert before <= a_before_touch <= after

    a.touch()
    after_touch = time.time()
    a_after_touch = a.getmtime()

    assert a_before_touch <= a_after_touch
    assert a_after_touch >= after
    assert a_after_touch <= after_touch

但它一直失败（https://travis-ci.org/datakortet/dkfileutils/builds），运行68：

>           assert before <= a_before_touch <= after
E           assert 1489532961.064958 <= 1489532961.064464

运行67

>           assert a_after_touch > after
E           assert 1489532462.412086 > 1489532462.412933

运行66

>           assert a_after_touch > after
E           assert 1489532286.6042855 > 1489532286.606766

假设time.time（）和file.getmtime（）是相关的，我真的很傻吗？

Answer 1

所有文件系统仅分配有限数量的位来存储文件时间戳;在一些较旧的文件系统中，分辨率是一秒或更差。一般来说，它永远不会给你与直接读时钟相同的分辨率。

time.time（）和file.getmtime（）之间的关系？

1 个答案: