regression test for new sequence unpacking semantics

Lib/test/test_unpack.py

+from test_support import *
+
+t = (1, 2, 3)
+l = [4, 5, 6]
+
+class Seq:
+    def __getitem__(self, i):
+	if i >= 0 and i < 3: return i
+	raise IndexError
+
+a = -1
+b = -1
+c = -1
+
+# unpack tuple
+if verbose:
+    print 'unpack tuple'
+a, b, c = t
+if a <> 1 or b <> 2 or c <> 3:
+    raise TestFailed
+
+# unpack list
+if verbose:
+    print 'unpack list'
+a, b, c = l
+if a <> 4 or b <> 5 or c <> 6:
+    raise TestFailed
+
+# unpack implied tuple
+if verbose:
+    print 'unpack implied tuple'
+a, b, c = 7, 8, 9
+if a <> 7 or b <> 8 or c <> 9:
+    raise TestFailed
+
+# unpack string... fun!
+if verbose:
+    print 'unpack string'
+a, b, c = 'one'
+if a <> 'o' or b <> 'n' or c <> 'e':
+    raise TestFailed
+
+# unpack generic sequence
+if verbose:
+    print 'unpack sequence'
+a, b, c = Seq()
+if a <> 0 or b <> 1 or c <> 2:
+    raise TestFailed
+
+# now for some failures
+
+# unpacking non-sequence
+if verbose:
+    print 'unpack non-sequence'
+try:
+    a, b, c = 7
+    raise TestFailed
+except TypeError:
+    pass
+
+
+# unpacking tuple of wrong size
+if verbose:
+    print 'unpack tuple wrong size'
+try:
+    a, b = t
+    raise TestFailed
+except ValueError:
+    pass
+
+# unpacking list of wrong size
+if verbose:
+    print 'unpack list wrong size'
+try:
+    a, b = l
+    raise TestFailed
+except ValueError:
+    pass
+
+
+# unpacking sequence too short
+if verbose:
+    print 'unpack sequence too short'
+try:
+    a, b, c, d = Seq()
+    raise TestFailed
+except ValueError:
+    pass
+
+
+# unpacking sequence too long
+if verbose:
+    print 'unpack sequence too long'
+try:
+    a, b = Seq()
+    raise TestFailed
+except ValueError:
+    pass
+
+
+# unpacking a sequence where the test for too long raises a different
+# kind of error
+BozoError = 'BozoError'
+
+class BadSeq:
+    def __getitem__(self, i):
+	if i >= 0 and i < 3:
+	    return i
+	elif i == 3:
+	    raise BozoError
+	else:
+	    raise IndexError
+
+
+# trigger code while not expecting an IndexError
+if verbose:
+    print 'unpack sequence too long, wrong error'
+try:
+    a, b, c, d, e = BadSeq()
+    raise TestFailed
+except BozoError:
+    pass
+
+# trigger code while expecting an IndexError
+if verbose:
+    print 'unpack sequence too short, wrong error'
+try:
+    a, b, c = BadSeq()
+    raise TestFailed
+except BozoError:
+    pass