first commit - distance between two cities

Author: dabillox

citydistance.py

@@ -0,0 +1,64 @@
+'''
+Work out the distance (user specified units) given two cities using haversine equation
+'''
+
+from pygeocoder import Geocoder
+import numpy as np
+import sys
+
+def get_distance(locA, locB):
+    #use haversine forumla
+    earth_rad = 6371.0
+    dlat = np.deg2rad(locB[0] - locA[0])
+    dlon = np.deg2rad(locB[1] - locA[1])
+    a = np.sin(dlat/2) * np.sin(dlat/2) + \
+        np.cos(np.deg2rad(locA[0])) * np.cos(np.deg2rad(locB[0])) * \
+        np.sin(dlon/2) * np.sin(dlon/2) 
+    c = 2 * np.arctan2(np.sqrt(a), np.sqrt(1-a))
+    return earth_rad * c 
+
+def get_latlongs(location):
+    return Geocoder.geocode(location)[0].coordinates
+        
+def convert_km_to_miles(km):
+    miles_per_km = 0.621371192
+    return km * miles_per_km
+    
+def main():
+    #get first city
+    print 'Type the first City: '
+    cityA = raw_input()
+    
+    #get second city
+    print 'Type the second city: '
+    cityB = raw_input()
+    
+    #get units
+    units = ''
+    while (units != 'km') & (units != 'm'):
+        print 'Type distance units (miles or kilometers): '
+        units = str.lower(raw_input())
+        if units in ['clicks', 'km', 'kilometers', 'kilometer']:
+            units = 'km'
+        elif units in ['m', 'mile', 'miles']:
+            units = 'm'
+        else:
+            print 'units not recognised, please try again'
+            
+    #find the distance in km
+    try:
+        distance = get_distance(get_latlongs(cityA),
+                                get_latlongs(cityB))
+        #display the distance
+        if units == 'km':
+            print str(distance),' km'   
+        else:
+            distance = convert_km_to_miles(distance)
+            print str(distance), ' miles' 
+            
+    except:
+        print 'Error raised.  Are the input cities correct?'
+        
+            
+if __name__ == '__main__':
+    sys.exit(main())