Small changes to map() and filter():

(1) If a sequence S is shorter than len(S) indicated, don't fail --
just use the shorter size.  (I.e, len(S) is just a hint.)

(2) Implement the special case map(None, S) as list(S) -- it's faster.

1 files changed, 8 insertions, 5 deletions

diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 775c318..63531db 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -190,8 +190,6 @@ builtin_filter(self, args)
 		int ok;
 
 		if ((item = (*sqf->sq_item)(seq, i)) == NULL) {
-			if (i < len)
-				goto Fail_1;
 			if (PyErr_ExceptionMatches(PyExc_IndexError)) {
 				PyErr_Clear();
 				break;
@@ -784,6 +782,11 @@ builtin_map(self, args)
 	func = PyTuple_GetItem(args, 0);
 	n--;
 
+	if (func == Py_None && n == 1) {
+		/* map(None, S) is the same as list(S). */
+		return PySequence_List(PyTuple_GetItem(args, 1));
+	}
+
 	if ((seqs = PyMem_NEW(sequence, n)) == NULL) {
 		PyErr_NoMemory();
 		goto Fail_2;
@@ -820,7 +823,6 @@ builtin_map(self, args)
 	if ((result = (PyObject *) PyList_New(len)) == NULL)
 		goto Fail_2;
 
-	/* XXX Special case map(None, single_list) could be more efficient */
 	for (i = 0; ; ++i) {
 		PyObject *alist, *item=NULL, *value;
 		int any = 0;
@@ -840,8 +842,6 @@ builtin_map(self, args)
 			else {
 				item = (*sqp->sqf->sq_item)(sqp->seq, i);
 				if (item == NULL) {
-					if (i < sqp->len)
-						goto Fail_0;
 					if (PyErr_ExceptionMatches(
 						PyExc_IndexError))
 					{
@@ -897,6 +897,9 @@ builtin_map(self, args)
 		}
 	}
 
+	if (i < len && PyList_SetSlice(result, i, len, NULL) < 0)
+		goto Fail_1;
+
 	PyMem_DEL(seqs);
 	return result;