Get POSIX/Unix time in seconds and nanoseconds in Python?

Since Python 3.7 it's easy to achieve with time.time_ns()

Similar to time() but returns time as an integer number of nanoseconds since the epoch.

All new features that includes nanoseconds in Python 3.7 release: PEP 564: Add new time functions with nanosecond resolution

Your precision is just being lost due to string formatting:

>>> import time
>>> print "%.20f" % time.time()
1267919090.35663390159606933594

It depends on the type of clock and your OS and hardware wether or not you can even get nanosecond precision at all. From the time module documentation:

The precision of the various real-time functions may be less than suggested by the units in which their value or argument is expressed. E.g. on most Unix systems, the clock “ticks” only 50 or 100 times a second.

On Python 3, the time module gives you access to 5 different types of clock, each with different properties; some of these may offer you nanosecond precision timing. Use the time.get_clock_info() function to see what features each clock offers and what precision time is reported in.

On my OS X 10.11 laptop, the features available are:

>>> for name in ('clock', 'monotonic', 'perf_counter', 'process_time', 'time'):
...     print(name, time.get_clock_info(name), sep=': ')
...
clock: namespace(adjustable=False, implementation='clock()', monotonic=True, resolution=1e-06)
monotonic: namespace(adjustable=False, implementation='mach_absolute_time()', monotonic=True, resolution=1e-09)
perf_counter: namespace(adjustable=False, implementation='mach_absolute_time()', monotonic=True, resolution=1e-09)
process_time: namespace(adjustable=False, implementation='getrusage(RUSAGE_SELF)', monotonic=True, resolution=1e-06)
time: namespace(adjustable=True, implementation='gettimeofday()', monotonic=False, resolution=1e-06)

so using the time.monotonic() or time.perf_counter() functions would theoretically give me nanosecond resolution. Neither clock gives me wall time, only elapsed time; the values are otherwise arbitrary. They are however useful for measuring how long something took.