gh-148085: datetime cache time module lookups

Misc/NEWS.d/next/Library/2026-04-04-14-25-43.gh-issue-148085.o97yTo.rst

@@ -0,0 +1,5 @@
+Cache ``time.struct_time``, and ``time.strftime`` imports, speeding up
+:meth:`~datetime.date.timetuple` and :meth:`~datetime.date.strftime` by up to
+2x. As such, patching :mod:`time` functions after importing :mod:`datetime`
+will no longer affect :mod:`datetime` behaviour. Patch by Maurycy
+Pawłowski-Wieroński.

Modules/_datetimemodule.c

@@ -52,6 +52,9 @@ typedef struct {
 
  /* The interned Unix epoch datetime instance */
  PyObject *epoch;
+
+ PyObject *time_struct_time;
+ PyObject *time_strftime;
 } datetime_state;
 
 /* The module has a fixed number of static objects, due to being exposed
@@ -1879,10 +1882,12 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
  assert(object && format && timetuple);
  assert(PyUnicode_Check(format));
 
- PyObject *strftime = PyImport_ImportModuleAttrString("time", "strftime");
- if (strftime == NULL) {
+ PyObject *current_mod = NULL;
+ datetime_state *st = GET_CURRENT_STATE(current_mod);
+ if (st == NULL) {
  return NULL;
  }
+ PyObject *strftime = st->time_strftime;
 
  /* Scan the input format, looking for %z/%Z/%f escapes, building
  * a new format. Since computing the replacements for those codes
@@ -2042,7 +2047,7 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
  Py_XDECREF(zreplacement);
  Py_XDECREF(colonzreplacement);
  Py_XDECREF(Zreplacement);
-Py_XDECREF(strftime);
+RELEASE_CURRENT_STATE(st, current_mod);
  return result;
 
  Error:
@@ -2055,41 +2060,26 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
  * from C. Perhaps they should be.
  */
 
-/* Call time.time() and return its result (a Python float). */
-static PyObject *
-time_time(void)
-{
- PyObject *result = NULL;
- PyObject *time = PyImport_ImportModuleAttrString("time", "time");
-
- if (time != NULL) {
- result = PyObject_CallNoArgs(time);
- Py_DECREF(time);
- }
- return result;
-}
-
 /* Build a time.struct_time. The weekday and day number are automatically
  * computed from the y,m,d args.
  */
 static PyObject *
 build_struct_time(int y, int m, int d, int hh, int mm, int ss, int dstflag)
 {
- PyObject *struct_time;
- PyObject *result;
-
- struct_time = PyImport_ImportModuleAttrString("time", "struct_time");
- if (struct_time == NULL) {
+ PyObject *current_mod = NULL;
+ datetime_state *st = GET_CURRENT_STATE(current_mod);
+ if (st == NULL) {
  return NULL;
  }
 
- result = PyObject_CallFunction(struct_time, "((iiiiiiiii))",
+ PyObject *result = PyObject_CallFunction(st->time_struct_time,
+ "((iiiiiiiii))",
  y, m, d,
  hh, mm, ss,
  weekday(y, m, d),
  days_before_month(y, m) + d,
  dstflag);
-Py_DECREF(struct_time);
+RELEASE_CURRENT_STATE(st, current_mod);
  return result;
 }
 
@@ -3311,7 +3301,11 @@ datetime_date_today_impl(PyTypeObject *type)
  type);
  }
 
- PyObject *time = time_time();
+ PyTime_t ts;
+ if (PyTime_Time(&ts) < 0) {
+ return NULL;
+ }
+ PyObject *time = PyFloat_FromDouble(PyTime_AsSecondsDouble(ts));
  if (time == NULL) {
  return NULL;
  }
@@ -7414,6 +7408,8 @@ init_state(datetime_state *st, PyObject *module, PyObject *old_module)
  .us_per_week = Py_NewRef(st_old->us_per_week),
  .seconds_per_day = Py_NewRef(st_old->seconds_per_day),
  .epoch = Py_NewRef(st_old->epoch),
+ .time_struct_time = Py_XNewRef(st_old->time_struct_time),
+ .time_strftime = Py_XNewRef(st_old->time_strftime),
  };
  return 0;
  }
@@ -7458,6 +7454,15 @@ init_state(datetime_state *st, PyObject *module, PyObject *old_module)
  return -1;
  }
 
+ st->time_struct_time = PyImport_ImportModuleAttrString("time", "struct_time");
+ if (st->time_struct_time == NULL) {
+ return -1;
+ }
+ st->time_strftime = PyImport_ImportModuleAttrString("time", "strftime");
+ if (st->time_strftime == NULL) {
+ return -1;
+ }
+
  return 0;
 }
 
@@ -7467,6 +7472,9 @@ traverse_state(datetime_state *st, visitproc visit, void *arg)
  /* heap types */
  Py_VISIT(st->isocalendar_date_type);
 
+ Py_VISIT(st->time_struct_time);
+ Py_VISIT(st->time_strftime);
+
  return 0;
 }
 
@@ -7482,6 +7490,8 @@ clear_state(datetime_state *st)
  Py_CLEAR(st->us_per_week);
  Py_CLEAR(st->seconds_per_day);
  Py_CLEAR(st->epoch);
+ Py_CLEAR(st->time_struct_time);
+ Py_CLEAR(st->time_strftime);
  return 0;
 }