7.3.MULTI-WAY DECISIONS 107

no yes

Calculate roots Print "no roots"

discrim < 0?

Figure7.3:Quadraticsolverasa two-waydecision.

quadratic3.py

import math

def main():
print "This programfinds the real solutions to a quadratic\n"
a, b, c = input("Please enter the coefficients (a, b, c): ")

discrim = b * b - 4 * a * c

if discrim < 0:

print "\nTheequation has no real roots!"

else:

discRoot = math.sqrt(b* b - 4 * a * c)

root1 = (-b + discRoot)/ (2 * a)

root2 = (-b - discRoot)/ (2 * a)

print

print "\nThesolutions are:", root1, root2

Thisprogramfitsthebillnicely. Hereis a samplesessionthatrunsthenew programtwice.

quadratic3.main()
This program findsthe real solutions to a quadratic

Please enter the coefficients(a, b, c): 1,2,3

The equation has no realroots!

quadratic3.main()
This program findsthe real solutions to a quadratic

Please enter the coefficients(a, b, c): 2,4,1

The solutions are:-0.292893218813 -1.70710678119

7.3 Multi-WayDecisions

Thenewestversionofthequadraticsolveris certainlya bigimprovement,butit stillhassomequirks.Here
is anotherexamplerun.