Subprocess in Python giving error!!!

Starting with the Basic code

a =  -2

b =  0.0

c =  0.0

total =  0

1360238044.98

a =  -2.0

b =  1.02

c =  0.51

total =  0.0

1360238048.01

Traceback (most recent call last):
  File "C:/AKS/Subprocess/ex_prog01.py", line 43, in <module>
    root = Myprog()
  File "C:/AKS/Subprocess/ex_prog01.py", line 9, in __init__
    self.Task_03()
  File "C:/AKS/Subprocess/ex_prog01.py", line 38, in Task_03
    q = subprocess.Popen(self.Task_02())
  File "C:\Python27\lib\subprocess.py", line 679, in __init__
    errread, errwrite)
  File "C:\Python27\lib\subprocess.py", line 852, in _execute_child
    args = list2cmdline(args)
  File "C:\Python27\lib\subprocess.py", line 580, in list2cmdline
    for arg in seq:
TypeError: 'NoneType' object is not iterable

import subprocess, time


class Myprog:

    def __init__(self,master=None):
        self.Task_03()
       

    def Task_01(self):
        v1 = 'Hello there'
        for x in range(1):
            time.sleep(2)
            print "\n", v1
        

    def Task_02(self):
        a = 1
        b = 1
        c = 1
        for i in range(2):
            total = ( a + b ) * c / (a + b + c)
            a = total - 2
            c = i * 0.51
            b = 2 * c
            time.sleep(3)
            print "\na = ", a
            print "\nb = ", b
            print "\nc = ", c
            print "\ntotal = ", total
            print "\n", time.time()
            

    def Task_03(self):
        print "\nStarting with the Basic code"
        q = subprocess.Popen(self.Task_02())
        p = subprocess.Popen(self.Task_01())
        print "\n\t\t\t\tEnd!!!!!"


root = Myprog()
root.mainloop()

import time

a = 1
b = 1
c = 1
for i in range(2):
    total = ( a + b ) * c / (a + b + c)
    a = total - 2
    c = i * 0.51
    b = 2 * c
    time.sleep(3)
    print "\na = ", a
    print "\nb = ", b
    print "\nc = ", c
    print "\ntotal = ", total
    print "\n", time.time()