Implement sys._getframe (#362)

Author: m4ns0ur

lib/sys.py

@@ -71,3 +71,13 @@ def exc_info():
 
 def exit(code=None):  # pylint: disable=redefined-builtin
   raise SystemExit(code)
+
+
+def _getframe(depth=0):
+  f = __frame__()
+  while depth > 0 and f is not None:
+    f = f.f_back
+    depth -= 1
+  if f is None:
+    raise ValueError('call stack is not deep enough')
+  return f

lib/sys_test.py

@@ -86,6 +86,23 @@ def TestExitInvalidArgs():
     assert False
 
 
+def TestGetFrame():
+  try:
+    sys._getframe(42, 42)
+  except TypeError:
+    pass
+  else:
+    assert False
+  try:
+    sys._getframe(2000000000)
+  except ValueError:
+    pass
+  else:
+    assert False
+  assert sys._getframe().f_code.co_name == '_getframe'
+  assert sys._getframe(1).f_code.co_name == 'TestGetFrame'
+
+
 if __name__ == '__main__':
   # This call will incidentally test sys.exit().
   weetest.RunTests()