add a custom __repr__ method for inertial frame objects

Author: jamesgrimmett

skyfield/documentation/earth-satellites.rst

@@ -532,7 +532,7 @@ for the satellite position, then use the frame to define an attitude vector:
 
 .. testoutput::
 
-    Frame: <skyfield.framelib.LVLH object at 0x7fd11ab18790>
+    Frame: <LVLH> Center (399) Pointing Local Vertical Local Horizontal reference frame.
     Attitude: [ 0.57745914  0.2781511  -0.76757599]
 
 In this case we have set the pitch and roll to zero, so the attitude vector
@@ -541,12 +541,14 @@ anti-aligned with the position vector:
 
 .. testcode::
 
+    from skyfield.functions import length_of
+
     neg_position = -geocentric.position.au / length_of(geocentric.position.au)
     print(neg_position)
 
 .. testoutput::
 
-    [0.57745914  0.2781511  -0.76757599]
+    [ 0.57745914  0.2781511  -0.76757599]
 
 Now, to find the intersection of this vector with the Earth’s surface we can
 use the :meth:`~skyfield.toposlib.Geoid.intersection_of()` method:

skyfield/framelib.py

@@ -149,6 +149,9 @@ def __init__(self, doc, matrix):
         self.__doc__ = doc
         self._matrix = matrix
 
+    def __repr__(self):
+        return '<{0}> {1}'.format(self.__class__.__name__, self.__doc__)
+
     def rotation_at(self, t):
         return self._matrix
 
@@ -170,7 +173,7 @@ def __init__(self, position):
         matrix = mxmxm(matrix, rot_z(pi - i), rot_y(-u))
 
         doc = (
-            "Center {0} Pointing Local Vertical Local Horizontal"
+            "Center ({0}) Pointing Local Vertical Local Horizontal"
             " reference frame."
             ).format(position.center)
         super(LVLH, self).__init__(doc, matrix)

skyfield/toposlib.py

@@ -286,7 +286,7 @@ def intersection_of(self, position, direction):
         of the Earth. The direction should be an |xyz| unit vector. Returns a
         `GeographicPosition` giving the geodetic ``latitude`` and ``longitude``
         at the point that the ray intersects the surface of the Earth.
-    
+
         The main calculation implemented here is based on JPL's NAIF toolkit;
         https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/ellipses.html
         """