Method compare

src/objectprotocol.rs:100–146

Compares two Python objects. On Python 2, this is equivalent to the Python expression 'cmp(self, other)'. On Python 3, this is equivalent to: ```ignore if self == other: return Equal elif a < b: return Less elif a > b: return Greater else: raise TypeError("ObjectProtocol::compare(): All comparisons returned false") ```

(&self, py: Python, other: O)

    ///     raise TypeError("ObjectProtocol::compare(): All comparisons returned false")
    /// ```
    fn compare<O>(&self, py: Python, other: O) -> PyResult<Ordering>
    where
        O: ToPyObject,
    {
        #[cfg(feature = "python27-sys")]
        unsafe fn do_compare(
            py: Python,
            a: *mut ffi::PyObject,
            b: *mut ffi::PyObject,
        ) -> PyResult<Ordering> {
            let mut result = -1;
            err::error_on_minusone(py, ffi::PyObject_Cmp(a, b, &mut result))?;
            Ok(result.cmp(&0))
        }

        #[cfg(feature = "python3-sys")]
        unsafe fn do_compare(
            py: Python,
            a: *mut ffi::PyObject,
            b: *mut ffi::PyObject,
        ) -> PyResult<Ordering> {
            let result = ffi::PyObject_RichCompareBool(a, b, ffi::Py_EQ);
            if result == 1 {
                return Ok(Ordering::Equal);
            } else if result < 0 {
                return Err(PyErr::fetch(py));
            }
            let result = ffi::PyObject_RichCompareBool(a, b, ffi::Py_LT);
            if result == 1 {
                return Ok(Ordering::Less);
            } else if result < 0 {
                return Err(PyErr::fetch(py));
            }
            let result = ffi::PyObject_RichCompareBool(a, b, ffi::Py_GT);
            if result == 1 {
                return Ok(Ordering::Greater);
            } else if result < 0 {
                return Err(PyErr::fetch(py));
            }
            Err(PyErr::new::<crate::exc::TypeError, _>(
                py,
                "ObjectProtocol::compare(): All comparisons returned false",
            ))
        }

        other.with_borrowed_ptr(py, |other| unsafe { do_compare(py, self.as_ptr(), other) })
    }

    /// Compares two Python objects.
    ///