Modules/timemodule.c (part 8)

Source:

cpython 3.14 @ ab2d84fe1023/Modules/timemodule.c ↗

This annotation covers high-resolution timers and time.sleep. See modules_time7_detail for time.time, time.gmtime, time.localtime, and time.strftime.

Map

Lines	Symbol	Role
1-80	time.sleep	Sleep for a fractional number of seconds
81-160	time.monotonic	Monotonically increasing clock
161-240	time.perf_counter	Highest resolution timer for benchmarking
241-320	time.process_time	CPU time consumed by the current process
321-500	_PyTime_t internals	Internal nanosecond representation

Reading

time.sleep

// CPython: Modules/timemodule.c:420 time_sleep
static PyObject *
time_sleep(PyObject *module, PyObject *obj)
{
    _PyTime_t timeout;
    if (_PyTime_FromSecondsObject(&timeout, obj, _PyTime_ROUND_TIMEOUT) < 0)
        return NULL;
    if (timeout < 0) {
        PyErr_SetString(PyExc_ValueError, "sleep length must be non-negative");
        return NULL;
    }
    if (pysleep(timeout) != 0)
        return NULL;
    Py_RETURN_NONE;
}

time.sleep(0.001) sleeps for 1 ms. On Unix, pysleep calls select or clock_nanosleep; on Windows it calls WaitForSingleObjectEx. The sleep is interruptible by signals (which set errno = EINTR).

time.monotonic

// CPython: Modules/timemodule.c:560 time_monotonic
static PyObject *
time_monotonic(PyObject *module, PyObject *unused)
{
    _PyTime_t t;
    if (_PyTime_GetMonotonicClock(&t) < 0)
        return NULL;
    return _PyFloat_FromTime_t(t);
}

time.monotonic() uses CLOCK_MONOTONIC on Linux/macOS and QueryPerformanceCounter on Windows. It never goes backward and is not affected by system clock adjustments. Use it for measuring elapsed time.

time.perf_counter

// CPython: Modules/timemodule.c:600 time_perf_counter
static PyObject *
time_perf_counter(PyObject *module, PyObject *unused)
{
    _PyTime_t t;
    if (_PyTime_GetPerfCounter(&t) < 0)
        return NULL;
    return _PyFloat_FromTime_t(t);
}

time.perf_counter() uses the highest-resolution timer available. On most platforms this is the same as monotonic. The reference point is undefined; only differences are meaningful.

_PyTime_t internals

// CPython: Modules/timemodule.c:80 (comment)
/* _PyTime_t is a signed 64-bit integer counting nanoseconds.
   Range: about ±292 years.
   Conversion:
     seconds   → _PyTime_t: multiply by 10^9
     _PyTime_t → float:     divide by 10^9 (may lose precision)
   _PyTime_ROUND_FLOOR, _CEILING, _HALF_EVEN, _TIMEOUT control rounding. */

All internal time values are nanoseconds in a int64_t. Floating-point seconds are converted at the API boundary. _PyTime_ROUND_TIMEOUT rounds up so that sleep(0.001) sleeps at least 1 ms.

gopy notes

time.sleep is module/time.Sleep in module/time/module.go using time.Sleep(d) from Go's time package. time.monotonic uses time.Now().UnixNano() with a baseline. time.perf_counter uses runtime.nanotime() via time.Now(). _PyTime_t maps to Go's int64 nanoseconds.