tutorial example

[Max Erickson]

>>> import math
>>> def distance1(x1, y1, x2, y2): 
   dx = x2 - x1 
   dy = y2 - y1 
   dsquared = dx**2 + dy**2 
   result = math.sqrt(dsquared) 
   print result
   return result

>>> def distance2(x1, y1, x2, y2): 
   dx = x2 - x1 
   dy = y2 - y1 
   dsquared = dx**2 + dy**2 
   result = math.sqrt(dsquared) 
   print result

 
They don't do the same thing here...
  
>>> distance1(1,2,3,4)
2.82842712475
2.8284271247461903
>>> distance2(1,2,3,4)
2.82842712475


the 'return result' line passes the result object in the function 
back to where the function was called. Functions without a return 
statement  default to returning 'None'. Calling the functions within 
a print statement illustrates the difference:

>>> print distance1(1,2,3,4)
2.82842712475
2.82842712475
>>> print distance2(1,2,3,4)
2.82842712475
None
>>> 

As you can see, distance2 does not actually return the result of the 
calculation to the interactive prompt...

max