#On the name of ALLAH
#Author : Fouad Teniou
#Date : 07/03/09
#version :2.6.1
""" New in python 2.6 namedtuple function is used in my program IRR-Versus-NPV
with a PresentValue as a typename, and discount rates r_1, r_2 and
number of periods until payments n as fieldnames (PresentValue('r_1','r_2','n'))
IRR-Versus-NPV program provide an NPV and IRR (linear interpolation)
calculations by entering the outflows/inflows values for a project
with 2 different rates r_1 and r_2, and only an NPV if r_2 is equal to zero
The program also returns any value or a series of values from the Present Value
Annuity Tables
"""
import itertools
import operator
import collections
import math as m
class MinusSignError(ArithmeticError):
""" user attempt an operation on negative number"""
pass
class PresentValue(collections.namedtuple('PresentValue', 'r_1,r_2,n')):
"""PresentValue a subclass of namedtuple Python class
with two rates values (r_1,r_2) and a period number n """
#set __slots__ to an empty tuple keep memory requirements low
__slots__ = ()
@property
def DF(self):
"""Compute the discount factor of two values"""
if self.r_1<0 or self.r_2 < 0 or self.n<0:
raise MinusSignError,\
"\n<Rates values and period number should be positive "
try:
discount_factor_1 = "%2.3f" % m.pow((1+self.r_1),-self.n)
discount_factor_2 = "%2.3f" % m.pow((1+self.r_2),-self.n)
return (discount_factor_1,discount_factor_2)
#DF raises Negative number error
except MinusSignError,exception:
print exception
@property
def AF(self):
"""Compute the annuity factor of two values"""
if self.r_1<0 or self.r_2 < 0 or self.n<0:
raise MinusSignError,\
"\n<Rates values and period number should be positive"
try:
annuity_factor_1 = "%2.3f" %((1-((m.pow((1+self.r_1),-self.n))))/self.r_1)
annuity_factor_2 = "%2.3f" %((1-((m.pow((1+self.r_2),-self.n))))/self.r_2)
return (annuity_factor_1,annuity_factor_2)
#AF raises Zero division number error
except ZeroDivisionError:
print "\n<Please choose a rate value greater than zero"
#AF raises Negative number error
except MinusSignError,exception:
print exception
def npvTable(self,*args):
"""Compute the NPV and IRR values of a project with two different rates"""
try:
#You need at least one rate to compute an NPV
assert self.r_1 !=0,"The first rate should not be equal to zero "
res_1 = []
res_2 = []
item_1 =[]
item_2 =[]
count_1 = -1
for arg in args:
count_1 +=1
#outflows/inflows starting at year 0
pv_set = PresentValue(r_1=self.r_1,r_2=self.r_2,n = count_1)
res_1.append(pv_set.DF[0]) # Trigger the Discount factor at rate r_1 and append the res_1
res_2.append(pv_set.DF[1]) # Trigger the Discount factor at rate r_2 and append the res_2
print "\n years \tCash flows \t DF at %s\t PV" %(str(int(self.r_1*100))+'%')
count_2 = -1
for (x_1,y) in (itertools.izip(res_1,args)): #for loop return PV set item_1
item_1.append((float(x_1)*y))
count_2 +=1
print "\n %s\t%s\t\t %s\t\t%s" %(count_2,y,x_1,int(float(x_1)*y))
npv_1 =(reduce(operator.add,item_1)) #Compute the npv_1 total
print '\n\t\t\t\t NPV = %s\n' % int(npv_1)
if self.r_2 == 0: #user attempt only one NPV calculation
print "<No NPV calculation %s=%s" % pv_set._asdict().items()[1]
else:
print "\n years \tCash flows \t DF at %s\t PV" %(str(int(self.r_2*100))+'%')
count_3 = -1
for (x_2,y) in (itertools.izip(res_2,args)): #for loop return PV set item_2
item_2.append((float(x_2)*y))
count_3 +=1
print "\n %s\t%s\t\t %s\t\t%s" %(count_3,y,x_2,int(float(x_2)*y))
npv_2 = (reduce(operator.add,item_2)) #Compute the npv_2 total
print '\n\t\t\t\t NPV = %s\n ' % int(npv_2)
#The IRR computation will depend of the rates and npvs (higher and lower values)
if self.r_1 > self.r_2:
print "<The IRR = %2.1f" % ((self.r_2+(npv_2/(npv_2-npv_1))*(self.r_1-self.r_2))*100)+' %\n'
else:
print "<The IRR = %2.1f" % ((self.r_1+(npv_1/(npv_1-npv_2))*(self.r_2-self.r_1))*100)+' %\n'
print "<The project will be recommended on finanacial grounds, while "
print "ignoring risk, if the IRR is greater than the target rate of "
print "return, otherwise the project will be rejected.\n"
#npvTable raises Negative number error
except MinusSignError,exception:
print exception
if __name__ == "__main__":
p = PresentValue('r_1','r_2','n')
p = p._replace(r_1=0.27,r_2 = 0.13)# n is equal to the numbers of outflows/inflows
p.npvTable(-70000,48000,24000,22000,13000,33000,15000,17000)
s = p._replace(r_1=0.07,r_2 =0.05) #You can set r_2 to zero to get only an NPV but not r_1 since you need at least one rate for the NPV
print " years\t\tDF at%2.0f%s\tAF at%2.0f%s\t DF at%2.0f%s\t AF at%2.0f%s \n" %\
(s.r_1*100,'%',s.r_1*100,'%',s.r_2*100,'%',s.r_2*100,'%')
for i in range(1,11): # you can do it individualy by setting r_1,r_2 and n (eg: PresentValue(r_1 = 0.17,r_2 = 0.07,n=7)
s = p._replace(r_1=0.07,r_2 =0.05,n=i)
print " %s\t\t%s\t\t %s\t\t %s\t\t %s" % \
(i,s.DF[0],s.AF[0],s.DF[1],s.AF[1])
# Another method to display the npv,for the same outflows/inflows values
# using different sets of rates and (n = to the number of outflows/inflows )
# It will save you time to write the same inflows/outflows every time you
# alter the rates
# below is just an example and you can extend your set of values as you wish.
a = [0.07,0.02,'n']
b = [0.04,0.05,'n']
c = [0.04,0.07,'n']
for item in a,b,c:
p = p._make(item)
p.npvTable(-70000,48000,24000,22000,13000,37000)
#Another way to retrieve Annuity factors and Discount factors
#individually or in sets of (r_1,r_2)
g = [0.04,0.07,17]
p = p._make(g)
print p.DF
print p.AF
print p.DF[0]
print p.DF[1]
print p.AF[0]
print p.AF[1]
#########################################################################################
# c:\Python26>python "C:Fouad Teniou\Documents\IRRvNPV.py"
# years Cash flows DF at 27% PV
# 0 -70000 1.000 -70000
# 1 28000 0.787 22036
# 2 24000 0.620 14880
# 3 22500 0.488 10980
# 4 13000 0.384 4992
# 5 33000 0.303 9999
# 6 15000 0.238 3570
# 7 17000 0.188 3196
# NPV = -347
# years Cash flows DF at 13% PV
# 0 -70000 1.000 -70000
# 1 28000 0.885 24780
# 2 24000 0.783 18792
# 3 22500 0.693 15592
# 4 13000 0.613 7969
# 5 33000 0.543 17919
# 6 15000 0.480 7200
# 7 17000 0.425 7225
# NPV = 29477
#<The IRR = 26.8 %
#<The project will be recommended on finanacial grounds, while
#ignoring risk, if the IRR is greater than the target rate of
#return, otherwise the project will be rejected.
# years DF at 7% AF at 7% DF at 5% AF at 5%
# 1 0.935 0.935 0.952 0.952
# 2 0.873 1.808 0.907 1.859
# 3 0.816 2.624 0.864 2.723
# 4 0.763 3.387 0.823 3.546
# 5 0.713 4.100 0.784 4.329
# 6 0.666 4.767 0.746 5.076
# 7 0.623 5.389 0.711 5.786
# 8 0.582 5.971 0.677 6.463
# 9 0.544 6.515 0.645 7.108
# 10 0.508 7.024 0.614 7.722
#c:\Python26>
###########################################################################################
