diff --git a/rust/indexes/src/errors.rs b/rust/indexes/src/errors.rs
--- a/rust/indexes/src/errors.rs
+++ b/rust/indexes/src/errors.rs
@@ -3,6 +3,9 @@
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 
+use cpython::{Python, PyErr};
+use cpython::exc::RuntimeError;
+
 error_chain! {
     foreign_links {
         Radix(::radixbuf::errors::Error);
@@ -14,3 +17,12 @@
         }
     }
 }
+
+/// Convert `Error` to Python `RuntimeError`s
+impl From<Error> for PyErr {
+    fn from(e: Error) -> PyErr {
+        let gil = Python::acquire_gil();
+        let py = gil.python();
+        PyErr::new::<RuntimeError, _>(py, format!("{}", e))
+    }
+}
diff --git a/rust/indexes/src/lib.rs b/rust/indexes/src/lib.rs
--- a/rust/indexes/src/lib.rs
+++ b/rust/indexes/src/lib.rs
@@ -14,3 +14,6 @@
 pub mod errors;
 pub mod nodemap;
 mod pybuf;
+
+#[allow(non_camel_case_types)]
+pub mod pyext;
diff --git a/rust/indexes/src/pyext.rs b/rust/indexes/src/pyext.rs
new file mode 100644
--- /dev/null
+++ b/rust/indexes/src/pyext.rs
@@ -0,0 +1,47 @@
+// Copyright 2017 Facebook, Inc.
+//
+// This software may be used and distributed according to the terms of the
+// GNU General Public License version 2 or any later version.
+
+use cpython::{PyResult, PyBytes, PyObject};
+use nodemap::NodeRevMap;
+use pybuf::SimplePyBuf;
+use std::slice;
+
+py_module_initializer!(indexes, initindexes, PyInit_indexes, |py, m| {
+    try!(m.add_class::<nodemap>(py));
+    Ok(())
+});
+
+py_class!(class nodemap |py| {
+    data nodemap: NodeRevMap<SimplePyBuf<u8>, SimplePyBuf<u32>>;
+
+    def __new__(_cls, changelog: &PyObject, index: &PyObject) -> PyResult<nodemap> {
+        let changelog_buf = SimplePyBuf::new(py, changelog);
+        let index_buf = SimplePyBuf::new(py, index);
+        let nm = NodeRevMap::new(changelog_buf, index_buf)?;
+        nodemap::create_instance(py, nm)
+    }
+
+    def __getitem__(&self, key: PyBytes) -> PyResult<Option<u32>> {
+        Ok(self.nodemap(py).node_to_rev(key.data(py))?)
+    }
+
+    def __contains__(&self, key: PyBytes) -> PyResult<bool> {
+        Ok(self.nodemap(py).node_to_rev(key.data(py))?.is_some())
+    }
+
+    def partialmatch(&self, hex: PyBytes) -> PyResult<Option<PyBytes>> {
+        Ok(self.nodemap(py).hex_prefix_to_node(hex.data(py))?.map(|b| PyBytes::new(py, b)))
+    }
+
+    def build(&self) -> PyResult<PyBytes> {
+        let buf = self.nodemap(py).build_incrementally()?;
+        let slice = unsafe { slice::from_raw_parts(buf.as_ptr() as *const u8, buf.len() * 4) };
+        Ok(PyBytes::new(py, slice))
+    }
+
+    def lag(&self) -> PyResult<u32> {
+        Ok(self.nodemap(py).lag())
+    }
+});