On 19/10/2020 12:42, Steve Dower wrote:
On 15Oct2020 2239, Rob Cliffe via Python-Dev wrote:
TLDR: In os.scandir directory entries, atime is always a copy of
mtime rather than the actual access time.
Correction - os.stat() updates the access time to _now_, while
os.scandir() returns the last access time without updating it.
Eryk replied with a deeper explanation of the cause, but fundamentally
this is what you are seeing.
Feel free to file a bug, but we'll likely only add a vague note to the
docs about how Windows works here rather than changing anything. If
anything, we should probably fix os.stat() to avoid updating the
access time so that both functions behave the same, but that might be
too complicated.
Cheers,
Steve
Sorry - what you say does not match the behaviour I observe, which is that
(1) Neither os.stat, nor reading os.scandir directory entries,
update any of the times on disk.
(2) os.stat.st_atime returns the "correct" time the file was last
accessed.
(3) os.scandir always returns st.atime equal to st.mtime.
Modified demo program:
# osscandirtest.py
import time, os
print(f'[1] {time.time()=}')
with open('Test', 'w') as f: f.write('Anything\n')
time.sleep(20)
print(f'[2] {time.time()=}')
with open('Test', 'r') as f: f.readline() # Read the file
time.sleep(10)
print(f'[3] {time.time()=}')
print(os.stat('Test'))
for DirEntry in os.scandir('.'):
if DirEntry.name == 'Test':
stat = DirEntry.stat()
print(f'scandir DirEntry {stat.st_ctime=} {stat.st_mtime=}
{stat.st_atime=}')
print(os.stat('Test'))
for DirEntry in os.scandir('.'):
if DirEntry.name == 'Test':
stat = DirEntry.stat()
print(f'scandir DirEntry {stat.st_ctime=} {stat.st_mtime=}
{stat.st_atime=}')
print(f'[4] {time.time()=}')
Sample output:
[1] time.time()=1603166161.12121
[2] time.time()=1603166181.1306772
[3] time.time()=1603166191.1426473
os.stat_result(st_mode=33206, st_ino=9851624184951253,
st_dev=2230120362, st_nlink=1, st_uid=0, st_gid=0, st_size=10,
st_atime=1603166181, st_mtime=1603166161, st_ctime=1603166161)
scandir DirEntry stat.st_ctime=1603166161.12121
stat.st_mtime=1603166161.12121 stat.st_atime=1603166161.12121
os.stat_result(st_mode=33206, st_ino=9851624184951253,
st_dev=2230120362, st_nlink=1, st_uid=0, st_gid=0, st_size=10,
st_atime=1603166181, st_mtime=1603166161, st_ctime=1603166161)
scandir DirEntry stat.st_ctime=1603166161.12121
stat.st_mtime=1603166161.12121 stat.st_atime=1603166161.12121
[4] time.time()=1603166191.1426473
You will observe that
(1) The results from the two os.stat calls are the same, as are the
results from the two scandir calls.
(2) The os.stat.st_atime (1603166181) *IS* the time that the file
was read with the
with open('Test', 'r') as f: f.readline() # Read the file
line of code, as it matches the
[2] time.time()=1603166181.1306772
line of output (apart from discarded fractions of a second) and
is 20 seconds (*not* 30 seconds) after the file creation time, as expected.
(3) The os.scandir atime is a copy of mtime (and in this case, of
ctime as well).
So it really does seem that the only thing "wrong" is that os.scandir
returns atime as a copy of mtime, rather than the correct value.
And since os.stat returns the "right" answer and os.scandir doesn't, it
really seems that this is a bug, or at least a deficiency, in os.scandir.
Demo run on Windows 10 Home version 1903 OS build 18362.1139
Python version 3.8.3 (32-bit).
Best wishes
Rob Cliffe
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