Significant speedup -- when a submodule imports a global module, add a
dummy entry to sys.modules, marking the absence of a submodule by the
same name.
Thus, if module foo.bar executes the statement "import time",
sys.modules['foo.time'] will be set to None, once the absence of a
module foo.time is confirmed (by looking for it in foo's path).
The next time when foo.bar (or any other submodule of foo) executes
"import time", no I/O is necessary to determine that there is no
module foo.time.
(Justification: It may seem strange to pollute sys.modules. However,
since we're doing the lookup anyway it's definitely the fastest
solution. This is the same convention that 'ni' uses and I haven't
heard any complaints.)
diff --git a/Python/import.c b/Python/import.c
index d62815e..a53abae 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -998,6 +998,7 @@
char *buf, int *p_buflen));
static PyObject *load_next Py_PROTO((PyObject *mod, PyObject *altmod,
char **p_name, char *buf, int *p_buflen));
+static int mark_miss Py_PROTO((char *name));
static int ensure_fromlist Py_PROTO((PyObject *mod, PyObject *fromlist,
char *buf, int buflen));
static PyObject * import_submodule Py_PROTO((PyObject *mod,
@@ -1168,11 +1169,17 @@
result = import_submodule(mod, p, buf);
if (result == Py_None && altmod != mod) {
Py_DECREF(result);
- /* Here, altmod must be None */
- strncpy(buf, name, len);
- buf[len] = '\0';
- *p_buflen = len;
- result = import_submodule(altmod, buf, buf);
+ /* Here, altmod must be None and mod must not be None */
+ result = import_submodule(altmod, name, name);
+ if (result != NULL && result != Py_None) {
+ if (mark_miss(buf) != 0) {
+ Py_DECREF(result);
+ return NULL;
+ }
+ strncpy(buf, name, len);
+ buf[len] = '\0';
+ *p_buflen = len;
+ }
}
if (result == NULL)
return NULL;
@@ -1188,6 +1195,14 @@
}
static int
+mark_miss(name)
+ char *name;
+{
+ PyObject *modules = PyImport_GetModuleDict();
+ return PyDict_SetItemString(modules, name, Py_None);
+}
+
+static int
ensure_fromlist(mod, fromlist, buf, buflen)
PyObject *mod;
PyObject *fromlist;