Closed as duplicate of#121376
Closed as duplicate of#121376
Description
Bug report
Bug description:
I found a problem when I change python source code real fast and execute it again. It looks like cpython uses the old cached bytecode when the timestamp of the bytecode and the timestamp of the new source are the same (it looks like the resolution is 1 second because it uses st_mtime).
The following code demonstrates the problem:
from subprocess import run
import sys
import time
with open("import_print_number.py", "w") as f:
f.write(
"""\
from print_number import print_number
print_number()
"""
)
for i in range(20):
print("test", i)
with open("print_number.py", "w") as f:
f.write(f"def print_number(): print({i})")
# low numbers make the bug more likely
time.sleep(0.6)
# run the code
result = run([sys.executable, "import_print_number.py"], capture_output=True)
n = int(result.stdout.decode().strip())
# numbers should be equal but are not in some cases,
# because python uses some old cached bytecode
assert i == n, (i, n)output (Python 3.11.2):
test 0
test 1
test 2
Traceback (most recent call last):
File "/home/frank/projects/pysource-playground/pysource-minimize/bug.py", line 28, in <module>
assert i == n, (i, n)
^^^^^^
AssertionError: (2, 1)My current work around is that i delete __pycache__ every time I change code but It would be nice if this is not neccessary. It is also really hard to figure out what is going on when it happens because the problem is often not deterministic.
CPython versions tested on:
3.11, 3.14, 3.13, 3.12, 3.10, 3.9
Operating systems tested on:
Linux