STINNER Victor <[email protected]> added the comment:
I would prefer to mimick importlib._bootstrap_external which uses:
def _pack_uint32(x):
"""Convert a 32-bit integer to little-endian."""
return (int(x) & 0xFFFFFFFF).to_bytes(4, 'little')
Using 64-bit timestamp (PR 19651), treat timestamp as unsigned (PR 9892 and PR
19708) have drawback:
* 64-bit timestamp make .pyc files larger
* unsigned timestamp no longer support timestamp before 1969 which can cause
practical issues
"& 0xFFFFFFFF" looks dead simple, uses a fixed size of 4 bytes and doesn't have
any limitation of year 2038.
The timestamp doesn't have to be exact. In practice, it sounds very unlikely
that two timestamps are equal when compared using (ts1 & 0xFFFFFFFF) == (ts2 &
0xFFFFFFFF). I expect file modification times to be close by a few days, not
separated by 2**32 seconds (136 years).
Use hash based .pyc to avoid any issuse with file modification time: it should
make Python more deterministic (more "reproducible").
https://docs.python.org/dev/reference/import.html#pyc-invalidation
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