PY: Added PlanetOrbitalPeriod function.

source/python/README.md

@@ -2345,6 +2345,20 @@ A pivoted matrix object.
 
 ---
 
+<a name="PlanetOrbitalPeriod"></a>
+### PlanetOrbitalPeriod(body)
+
+**Returns the average number of days it takes for a planet to orbit the Sun.**
+
+| Type | Parameter | Description |
+| --- | --- | --- |
+| [`Body`](#Body) | `body` | One of the planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, or Pluto. |
+
+**Returns**: `float`
+The mean orbital period of the body in days.
+
+---
+
 <a name="RefractionAngle"></a>
 ### RefractionAngle(refraction, altitude)
 

source/python/astronomy/astronomy.py

@@ -420,6 +420,23 @@ class NoConvergeError(Error):
     def __init__(self):
         Error.__init__(self, 'Numeric solver did not converge - please report issue at https://github.com/cosinekitty/astronomy/issues')
 
+def PlanetOrbitalPeriod(body):
+    """Returns the average number of days it takes for a planet to orbit the Sun.
+
+    Parameters
+    ----------
+    body : Body
+        One of the planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, or Pluto.
+
+    Returns
+    -------
+    float
+        The mean orbital period of the body in days.
+    """
+    if isinstance(body, Body) and (0 <= body.value < len(_PlanetOrbitalPeriod)):
+        return _PlanetOrbitalPeriod[body.value]
+    raise InvalidBodyError()
+
 def _SynodicPeriod(body):
     if body == Body.Earth:
         raise EarthNotAllowedError()