1 files changed, 77 insertions, 0 deletions
diff --git a/python/problems/lists_and_for/every_third/common.py b/python/problems/lists_and_for/every_third/common.py
new file mode 100644
index 0000000..2d5b907
--- /dev/null
+++ b/python/problems/lists_and_for/every_third/common.py
@@ -0,0 +1,77 @@
+# coding=utf-8
+
+import re
+from python.util import has_token_sequence, string_almost_equal, \
+    string_contains_number, get_tokens, get_numbers, get_exception_desc
+from server.hints import Hint
+
+id = 220
+number = 6
+visible = True
+
+solution = '''\
+xs = [42, 5, 4, -7, 2, 12, -3, -4, 11, 42, 2]
+
+ys = []
+i = 2
+while i < len(xs):
+    ys.append(xs[i])
+    i += 3
+print(ys)
+'''
+
+hint_type = {
+    'final_hint': Hint('final_hint')
+}
+
+def test(python, code):
+    in_out = [
+        ([], []),
+        ([0], []),
+        ([0, 1], []),
+        ([0, 1, 2], [2]),
+        ([1, 2, 3, 4, 5, 5, 4, 3, 2, 1], [3, 5, 2]),
+        ([42, 5, 4, -7, 2, 12, -3, -4, 11, 42, 2], [4, 12, 11]),
+        (list(range(15)), [2, 5, 8, 11, 14])
+    ]
+
+    test_in = [t[0] for t in in_out]
+    test_out = [t[1] for t in in_out]
+
+    n_correct = 0
+    tin = None
+    for xs_i, xs in enumerate(test_in):
+        # change code to contain new xs instead of the one
+        # given by user
+        tcode = re.sub(r'^xs\s*=\s*\[.*?\]',
+                       'xs = ' + str(xs),
+                       code,
+                       flags = re.DOTALL | re.MULTILINE)
+
+        # use python session to call tcode
+        answers = python(code=tcode, inputs=[(None, None)], timeout=1.0)
+        output = answers[0][1]
+
+        if str(test_out[xs_i]) in output:
+            n_correct += 1
+        else:
+            tin = test_in[xs_i]
+            tout = test_out[xs_i]
+    passed = n_correct == len(test_in)
+
+    hints = [{'id': 'test_results', 'args': {'passed': n_correct, 'total': len(test_in)}}]
+    if tin:
+        hints.append({'id': 'problematic_test_case', 'args': {'testin': str(tin), 'testout': str(tout)}})
+    if passed:
+        hints.append({'id': 'final_hint'})
+    return passed, hints
+
+def hint(python, code):
+    tokens = get_tokens(code)
+
+    # run one test first to see if there are any exceptions
+    answer = python(code=code, inputs=[(None, None)], timeout=1.0)
+    exc = get_exception_desc(answer[0][3])
+    if exc: return exc
+
+    return None