py: Fix mult by negative number of tuple, list, str, bytes.

Multiplication of a tuple, list, str or bytes now yields an empty
sequence (instead of crashing).  Addresses issue #799

Also added ability to mult bytes on LHS by integer.

4 files changed, 42 insertions, 2 deletions

diff --git a/tests/basics/bytes_mult.py b/tests/basics/bytes_mult.py
new file mode 100644
index 000000000..0effd938e
--- /dev/null
+++ b/tests/basics/bytes_mult.py
@@ -0,0 +1,12 @@
+# basic multiplication
+print(b'0' * 5)
+
+# check negative, 0, positive; lhs and rhs multiplication
+for i in (-4, -2, 0, 2, 4):
+    print(i * b'12')
+    print(b'12' * i)
+
+# check that we don't modify existing object
+a = b'123'
+c = a * 3
+print(a, c)
diff --git a/tests/basics/list_mult.py b/tests/basics/list_mult.py
index ec65fbb3f..16948f74c 100644
--- a/tests/basics/list_mult.py
+++ b/tests/basics/list_mult.py
@@ -1,4 +1,12 @@
+# basic multiplication
 print([0] * 5)
+
+# check negative, 0, positive; lhs and rhs multiplication
+for i in (-4, -2, 0, 2, 4):
+    print(i * [1, 2])
+    print([1, 2] * i)
+
+# check that we don't modify existing list
 a = [1, 2, 3]
 c = a * 3
-print(c)
+print(a, c)
diff --git a/tests/basics/string_mult.py b/tests/basics/string_mult.py
new file mode 100644
index 000000000..c0713c1d3
--- /dev/null
+++ b/tests/basics/string_mult.py
@@ -0,0 +1,12 @@
+# basic multiplication
+print('0' * 5)
+
+# check negative, 0, positive; lhs and rhs multiplication
+for i in (-4, -2, 0, 2, 4):
+    print(i * '12')
+    print('12' * i)
+
+# check that we don't modify existing object
+a = '123'
+c = a * 3
+print(a, c)
diff --git a/tests/basics/tuple_mult.py b/tests/basics/tuple_mult.py
index f8350f2f2..0f52bce44 100644
--- a/tests/basics/tuple_mult.py
+++ b/tests/basics/tuple_mult.py
@@ -1,4 +1,12 @@
+# basic multiplication
 print((0,) * 5)
+
+# check negative, 0, positive; lhs and rhs multiplication
+for i in (-4, -2, 0, 2, 4):
+    print(i * (1, 2))
+    print((1, 2) * i)
+
+# check that we don't modify existing tuple
 a = (1, 2, 3)
 c = a * 3
-print(c)
+print(a, c)