Tech Erudition

def functionCreator(choice):
   """Create the function and return it depending on choice."""
   if(choice==1):
       print "Create function for evaluating x*y+z ..."
       func = lambda x,y,z: x*y+z
   elif(choice==2):
       print "Create function for evaluating x*y-z ..."
       func = lambda x,y,z: x*y-z
   elif(choice==3):
       print "Create function for evaluating x*y*z ..."
       func = lambda x,y,z: x*y*z
   elif(choice==4):
       print "Create function for evaluating x*y**z ..."
       func = lambda x,y,z: x*y**z
   # return the generated function
   return func

# A class which defines a default function definition to evaulate its variables
# It also allows user to change the function definition at runtime so the class
# behaviour to evaulate its variables changes.
class Evaluate(object):
   """ Allow evaluation of 3 class variables with custom function at runtime."""

   def __init__(self,x,y,z):
       """Initializer which takes 3 variables x,y,z"""
       self.x = x #self.__dict__["x"] = x
       self.y = y #self.__dict__["x"] = y
       self.z = z #self.__dict__["x"] = z

   def evaluate(self,x,y,z):
       """ A default function definition to evaluate the variables.
       This function definition is configurable at runtime."""       
       return x+y+z

   def func(self):
       """ Call this function to evaluate the variables of the class
       This will delegate the work to evaluate function."""
       print "%s: %f" % ("Result",self.evaluate(self.x,self.y,self.z))

   def change(self):
       """ This function will allow user to configure the function definition
       of evaluate."""

       print "Available function generation for evaluating expression..."
       print "1. x*y+z"
       print "2. x*y-z"
       print "3. x*y*z"
       print "4. x*y**z"

       choice = int(raw_input("Please enter your choice(1,2,3,4): "))

       # Change the evaluate function defintion
       self.__dict__["evaluate"] = functionCreator(choice)

       # Inform user that the function definition was changed and can view the change
       print "Please try object.func() to see the change in evaluation."
     
# Testing for this module
if __name__ == "__main__":
   print "Evaluate Module loaded..."

>>> exeval=Evaluate(10,20,30)
>>> exeval.func()
Result: 60.000000
>>> exeval.change()
Available function generation for evaluating expression...
1. x*y+z
2. x*y-z
3. x*y*z
4. x*y**z
Please enter your choice(1,2,3,4): 1
Create function for evaluating x*y+z ...
Please try object.func() to see the change in evaluation.
>>> exeval.func()
Result: 230.000000
>>> exeval.change()
Available function generation for evaluating expression...
1. x*y+z
2. x*y-z
3. x*y*z
4. x*y**z
Please enter your choice(1,2,3,4): 2
Create function for evaluating x*y-z ...
Please try object.func() to see the change in evaluation.
>>> exeval.func()
Result: 170.000000
>>> exeval.change()
Available function generation for evaluating expression...
1. x*y+z
2. x*y-z
3. x*y*z
4. x*y**z
Please enter your choice(1,2,3,4): 3
Create function for evaluating x*y*z ...
Please try object.func() to see the change in evaluation.
>>> exeval.func()
Result: 6000.000000
>>> exeval.change()
Available function generation for evaluating expression...
1. x*y+z
2. x*y-z
3. x*y*z
4. x*y**z
Please enter your choice(1,2,3,4): 4
Create function for evaluating x*y**z ...
Please try object.func() to see the change in evaluation.
>>> exeval.func()
Result: 10737418239999999609046623630827404132352.000000
>>>