Use number of seconds since the UNIX Epoch as date format in logging

Question

The docs for logging.basicConfig say:

datefmt - Use the specified date/time format, as accepted by time.strftime().

However, if I have a look at the docs for time.strftime(), the UNIX Epoch timestamp isn't even mentioned there.

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Update: If I'm using %s as described in the manpage for strftime(3), it works with Linux, but not with Windows.

import time
time.strftime('%s')

results in

ValueError: Invalid format string

So I'm looking for a platform-independent way to use the number of seconds since the UNIX Epoch as date format in logging.

Answer 1

It's not possible to do this with asctime for certain, since the behavior of strftime regarding supported format strings is platform-dependent.

There is a paragraph in the docs in the section "strftime() and strptime() Behavior" about this:

The full set of format codes supported varies across platforms, because Python calls the platform C library’s strftime() function, and platform variations are common. To see the full set of format codes supported on your platform, consult the strftime(3) documentation.

https://docs.python.org/3/library/datetime.html#strftime-and-strptime-behavior

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However, disregarding asctime, you can still use the number of seconds since the UNIX Epoch in your logginng format string. There is another attribute called created:

%(created)f - Time when the LogRecord was created (as returned by time.time()).

https://docs.python.org/3/library/logging.html#logrecord-attributes

Since time.time() works on both Linux and Windows, you can just use created instead of asctime in the logging format string.