bpo-31415: Support PYTHONPROFILEIMPORTTIME envvar equivalent to -X importtime (#4240)

Support PYTHONPROFILEIMPORTTIME envvar equivalent to -X importtime

3 files changed, 25 insertions, 7 deletions

diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
index 8ab26f5955..310891d6d0 100644
--- a/Doc/using/cmdline.rst
+++ b/Doc/using/cmdline.rst
@@ -411,7 +411,8 @@ Miscellaneous options
    * ``-X importtime`` to show how long each import takes. It shows module name,
      cumulative time (including nested imports) and self time (exluding nested
      imports).  Note that its output may be broken in multi threaded application.
-     Typical usage is ``python3 -X importtime -c 'import asyncio'``.
+     Typical usage is ``python3 -X importtime -c 'import asyncio'``.  See also
+     :envvar:`PYTHONPROFILEIMPORTTIME`.
 
    It also allows passing arbitrary values and retrieving them through the
    :data:`sys._xoptions` dictionary.
@@ -429,7 +430,7 @@ Miscellaneous options
       The ``-X showalloccount`` option.
 
    .. versionadded:: 3.7
-      The ``-X importtime`` option.
+      The ``-X importtime`` and :envvar:`PYTHONPROFILEIMPORTTIME` options.
 
 
 Options you shouldn't use
@@ -650,6 +651,15 @@ conflict.
    .. versionadded:: 3.4
 
 
+.. envvar:: PYTHONPROFILEIMPORTTIME
+
+   If this environment variable is set to a non-empty string, Python will
+   show how long each import takes.  This is exactly equivalent to setting
+   ``-X importtime`` on the command line.
+
+   .. versionadded:: 3.7
+
+
 .. envvar:: PYTHONASYNCIODEBUG
 
    If this environment variable is set to a non-empty string, enable the
diff --git a/Misc/NEWS.d/3.7.0a2.rst b/Misc/NEWS.d/3.7.0a2.rst
index 6df77153a0..7784bb77be 100644
--- a/Misc/NEWS.d/3.7.0a2.rst
+++ b/Misc/NEWS.d/3.7.0a2.rst
@@ -166,7 +166,8 @@ special method lookups.  Patch by Stefan Behnel.
 .. section: Core and Builtins
 
 Add ``-X importtime`` option to show how long each import takes. It can be
-used to optimize application's startup time.
+used to optimize application's startup time.  Support the
+:envvar:`PYTHONPROFILEIMPORTTIME` as an equivalent way to enable this.
 
 ..
 
diff --git a/Python/import.c b/Python/import.c
index d396b4de79..7ba1842e75 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1682,10 +1682,17 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
          * _PyDict_GetItemId()
          */
         if (ximporttime == 0) {
-            PyObject *xoptions = PySys_GetXOptions();
-            if (xoptions) {
-                PyObject *value = _PyDict_GetItemId(xoptions, &PyId_importtime);
-                ximporttime = (value == Py_True);
+            char *envoption = Py_GETENV("PYTHONPROFILEIMPORTTIME");
+            if (envoption != NULL && strlen(envoption) > 0) {
+                ximporttime = 1;
+            }
+            else {
+                PyObject *xoptions = PySys_GetXOptions();
+                if (xoptions) {
+                    PyObject *value = _PyDict_GetItemId(
+                        xoptions, &PyId_importtime);
+                    ximporttime = (value == Py_True);
+                }
             }
             if (ximporttime) {
                 fputs("import time: self [us] | cumulative | imported package\n",