Modularized program to find circumference, diameter, and area from a circle's radius

Question

I have to create a modularized program that can find out the diameter, circumference, and area of a circle's radius. I'm sure many of you can notice I kind of winged this from a example given from my teacher. Instead of people pointing out the fact that I coded this wrong, could you please give me reasons for what I should do so I can better understand this concept?

import math

def main():
    Radius = 0
    Diameter = 0
    Circumference = 0
    Area = 0


    Radius = GetRadius(Radius)
    Diameter = SetDiameter(Radius, Diameter)
    Circumference = SetCircumference(Radius, Circumference)
    Area = SetArea(Radius, Area)
    ShowResults(Radius, Diameter, Circumference, Area)


def GetRadius(myradius):
    myradius = float(str(input("Enter your radius: ")))
    return myradius

def SetDiameter(myradius, mydiameter):
    mydiameter = myradius * 2
    return mydiameter

def SetCircumference(myradius, mycircumference):
    PIE = 3.14159
    mycircumference = 2 * PIE * myradius
    return mycircumference

def SetArea(myradius, myarea):
    PIE = 3.14159
    myarea = PIE * myradius * myradius
    return myarea

def ShowResults(Radius, Diameter, Circumference, Area):
    print("The Diameter is",mydiameter)
    print("The Circumference is",mycircumference)
    print("The Area is",myarea)

main()

Answer 1

Many little comments here to make things simpler,shorter,more pythonic :

• PEP 0008 gives some coding guidelines for python. Among other things, it gives a naming convention. Also, you don't need the "my" prefix everywhere.

• You can use math.pi instead of repeating our own definition of pi everywhere. (Isn't it the reason why your import math in the first place)

• Most of your function just need to return a value and updating the parameter probably shouldn't be their responsability.

• Most of the variables are not really required.

• there's no point to define a main function in your case.

After taking these comments into accounts, your code looks like this :

import math

def get_radius_from_user():
    return float(input("Enter your radius: "))

def get_diameter(radius):
    return radius * 2

def get_circumference(radius):
    return 2 * math.pi * radius

def get_area(radius):
    return math.pi * radius * radius

def show_results(radius):
    print("The Diameter is",get_diameter(radius))
    print("The Circumference is",get_circumference(radius))
    print("The Area is",get_area(radius))

show_results(get_radius_from_user())

Answer 2

Once you've learned about classes you could create a Circle object which when initiated performs all possible conversions, so that its properties - diameter, radius, area and circumference - can all be accessed without having to write anything else.

The conversion functions can be stored as a dictionary of lambdas.

import math
class Circle:
    conversions = {
        ('diameter', 'radius'): lambda d: d / 2.0,
        ('radius', 'area'): lambda r: math.pi * r ** 2,
        ('radius', 'diameter'): lambda r: r * 2.0,
        ('radius', 'circumference'): lambda r: math.pi * r * 2,
        ('area', 'radius'): lambda a: (a / math.pi) ** .5,
        ('circumference', 'radius'): lambda c: c / (math.pi * 2)
    }

    def _set(self, property, value):
        """ Set a property and recursively make all possible 
            conversions based on that property """    
        setattr(self, property, value)
        for (fro, to), conversion in self.conversions.items():
            if fro == property and getattr(self, to, None) is None:
                self._set(to, conversion(getattr(self, fro)))

    def __init__(self, **kwargs):
        self._set(*kwargs.items()[0])

my_circle = Circle(radius = 5)
print my_circle.area