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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.)
This commit is contained in:
Guido van Rossum 1997-09-06 20:29:52 +00:00
parent 81da02e6aa
commit f5f5fdbdd0
1 changed files with 20 additions and 5 deletions
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25
Python/import.c
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@ -998,6 +998,7 @@ static PyObject *get_parent Py_PROTO((PyObject *globals,
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 @@ load_next(mod, altmod, p_name, buf, p_buflen)
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;
@ -1187,6 +1194,14 @@ load_next(mod, altmod, p_name, buf, p_buflen)
return result;
}
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;