add print method to Body object

lib/class.py

@@ -1,20 +1,25 @@
-import numpy as np
-
+#!/usr/bin/python
+# -*- coding:utf-8 -*-
 """
 Class definition for physical atribute
 """
+import numpy as np
 
 
 class Body:
     
-
-    
     def __init__(self, mass, position, velocity):
         self.m = mass
         self.q = position
         self.v = velocity
         self.p = velocity*mass
 
+    def __repr__(self): # Called upon "print(body)"
+        return "Body of mass: {0:.2f}kg, position: {1}, velocity: {2}".format(self.m, self.p, self.v)
+    
+    def __str__(self): # Called upon "str(body)"
+        return "Body of mass: {0:.2f}kg, position: {1}, velocity: {2}".format(self.m, self.p, self.v)
+
 
 class System:
 
@@ -49,37 +54,35 @@ class System:
         return L
 
 
-    #def initialize(self):
+if __name__ == "__main__":        
+    # initialisation mass
+    m1 = 10
+    m2 = 1
+    m3 = 1
         
-# initialisation mass
-m1 = 10
-m2 = 1
-m3 = 1
+    # initialisation position
+    q1 = np.array([0, 0, 0])
+    q2 = np.array([1, 0, 0])
+    q3 = np.array([2, 0, 0])
 
-# initialisation position
-q1 = np.array([0, 0, 0])
-q2 = np.array([1, 0, 0])
-q3 = np.array([2, 0, 0])
-
-# initialisation velocity
-v1 = np.array([0, 0, 0])
-v2 = np.array([1, 1, 0])
-v3 = np.array([2, 0, 0])
+    # initialisation velocity
+    v1 = np.array([0, 0, 0])
+    v2 = np.array([1, 1, 0])
+    v3 = np.array([2, 0, 0])
 
 
-star1 = Body(m1,q1,v1)
-star2 = Body(m2,q2,v2)
-star3 = Body(m3,q3,v3)
+    star1 = Body(m1,q1,v1)
+    star2 = Body(m2,q2,v2)
+    star3 = Body(m3,q3,v3)
 
-Lbodylist = [star1,star2]
+    Lbodylist = [star1,star2]
 
-array = np.zeros((len(Lbodylist),3))
-array[0]=star3.q
+    array = np.zeros((len(Lbodylist),3))
+    array[0]=star3.q
 
 
-tribody = System([star1,star2,star3])
+    tribody = System([star1,star2,star3])
 
-print("list=",Lbodylist)
-
-print(tribody.Lval(Lbodylist))
+    print("list=",Lbodylist)
 
+    print(tribody.Lval(Lbodylist))