diff --git a/python/python_api.h b/python/python_api.h
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+++ b/python/python_api.h
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+/*
+ * Copyright (c) 2009-2021, Google LLC
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of Google LLC nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL Google LLC BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef PYUPB_PYTHON_H__
+#define PYUPB_PYTHON_H__
+
+// We restrict ourselves to the limited API, so that a single build can be
+// ABI-compatible with a wide range of Python versions.
+//
+// The build system will define Py_LIMITED_API as appropriate (see BUILD). We
+// only want to define it for our distribution packages, since we can do some
+// extra assertions when Py_LIMITED_API is not defined.  Also Py_LIMITED_API is
+// incompatible with Py_DEBUG.
+
+// #define Py_LIMITED_API <val>  // Defined by build system when appropriate.
+
+#include "Python.h"
+
+// Ideally we could restrict ourselves to the limited API of 3.7, but this is
+// a very important function that was not officially added to the limited API
+// until 3.10.  Without this function, there is no way of getting data from a
+// Python `str` object without a copy.
+//
+// While this function was not *officially* added to the limited API until
+// Python 3.10, In practice it has been stable since Python 3.1.
+//   https://bugs.python.org/issue41784
+//
+// On Linux, ELF lets us get away with using this function with the limited
+// API prior to 3.10.
+
+#if defined(__linux__) && defined(Py_LIMITED_API) && Py_LIMITED_API < 0x03100000
+PyAPI_FUNC(const char*)
+    PyUnicode_AsUTF8AndSize(PyObject* unicode, Py_ssize_t* size);
+#endif
+
+#endif  // PYUPB_PYTHON_H__