Fibonacci sequence creation in Rust to bind in Python

libfibonacci.rs

#[macro_use] extern crate cpython;

use std::vec::Vec;
use cpython::{PyResult, Python};

// add bindings to the generated python module
// N.B: names: "libfibonacci" must be the name of the `.so` or `.pyd` file
py_module_initializer!(libfibonacci, initlibfibonacci, PyInit_libfibonacci, |py, m| {
    try!(m.add(py, "__doc__", "Fibonacci sequence creation in Rust."));
    try!(m.add(py, "fibonacci", py_fn!(py, fibonacci_py(a: u64))));
    Ok(())
});

fn fibonacci(max: u64) -> Vec<u64> {
    let mut seq = Vec::new();
    let (mut a, mut b) = (0, 1);
    while a <= max {
        seq.push(a);
        let temp = a;
        a = b;
        b += temp;
    }
    seq
}

fn fibonacci_py(_: Python, max: u64) -> PyResult<Vec<u64>> {
    Ok(fibonacci(max))
}

repl.py

>>> import libfibonacci
>>> libfibonacci.fibonacci(100000)
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, 10946, 17711, 28657, 46368, 75025]
>>> help(libfibonacci)

Help on module libfibonacci

NAME
    libfibonacci - Fibonacci sequence creation in Rust.

FUNCTIONS
    fibonacci = fibonacci_py(...)

FILE
    /path/to/libfibonacci.so