Programming Forums > Script Programming > Python

acwbrat · Oct 30th, 2007, 9:43 PM

I have written a python code for quadratic formula

. However, I need both real and complex numbers for my results. I have done research and noticed two differences: real numbers uses import math and complex numbers uses import cmath

Here's my code. I would like to know what I have done wrong. I have even put my comments on there:

(Toggle Plain Text)

# quadraticcomplex.py
# A program that computes the complex roots of a quadratic equation.
# Illustrates use of the cmath library. 
# The presence of complex numbers also requires mathematical functions that can perform operations on them.
# The imaginary component of a complex number is denoted by a suffix of ``J'' or ``j'';

import cmath  # Makes the cmath library available.

def main(): # beginning of the code
    print "Hello! This program finds the complex solutions to a quadratic"
    print

    a, b, c = input("Please enter the coefficients (a, b, c): ")

    discRoot = cmath.sqrt(b * b - 4 * a * c) # formula solving discriminant
    root1 = (-b + discRoot) / (2 * a) # formula solving root1
    root2 = (-b - discRoot) / (2 * a) # formula solving root2

    print
    print "The solutions are:", root1, root2 # display the results

main() # end of the code

Sane · Oct 30th, 2007, 9:49 PM

Don't use cmath. Use math.

Sorry about that. Edit:

Just force it to be positive before you square root it, and then indicate that it's an imaginary number, calculating the real and imaginary portion how you normally would by hand.

(Toggle Plain Text)

    disc = b**2 - 4*a*c # discriminant
    if disc < 0:
        disc = -disc    # force it to be positive
    else:
        print "This quadratic does not have imaginary roots"
        return

    discRoot = math.sqrt(disc)

    root1r = (-b) / (2 * a)      # the real portion of root1
    root1i = discRoot / (2 * a)  # the imaginary portion of root1
    
    root2r = root1r      # the real portions are the same for each root
    root2i = -root1i     # the only difference is it's negative

So it's basically done how someone solving it with a pencil would do it. That's usually an ideal way of thinking about how to program a solution.

By the way, wrap your code in [code][/code] tags next time.

acwbrat · Oct 30th, 2007, 9:52 PM

Is this the same for real numbers too?

Sane · Oct 30th, 2007, 10:00 PM

[Delete]

Sane · Oct 30th, 2007, 10:03 PM

Sorry about that. I forgot that imaginary numbers are calculated in pieces when you use the quadratic formula. It's been too long.

My first post is now edited.

acwbrat · Oct 30th, 2007, 10:12 PM

Oh Thank you! Yes I am new to programming in python. I thought that the code was straight. But when I have noticed on import math, it would calculate the real numbers of the quadratic formula. I also thought that cmath would calculate complex numbers for quadratic formula. I thought in python, j represented complex numbers.

acwbrat · Oct 30th, 2007, 10:15 PM

So is this the correct format for the code?

(Toggle Plain Text)

 def main(): # beginning of the code
print "Hello! This program finds the complex solutions to a quadratic"
print

a, b, c = input("Please enter the coefficients (a, b, c): ")

disc = b**2 - 4*a*c # discriminant
    if disc < 0:
        disc = -disc    # force it to be positive
    else:
        print "This quadratic does not have imaginary roots"
        return

    discRoot = math.sqrt(disc)

    root1r = (-b) / (2 * a)      # the real portion of root1
    root1i = discRoot / (2 * a)  # the imaginary portion of root1
    
    root2r = root1r      # the real portions are the same for each root
    root2i = -root1i     # the only difference is it's negative

main()

Sane · Oct 30th, 2007, 10:19 PM

Yes, that should work, if you fix your indenting. And print out the output in a way the user can understand.

If you want it to be able to handle both real and imaginary roots, you'll basically need to split the program up into two parts. If the discriminant is less than 0, you use the end part of the code I gave you. Otherwise, you make it use the end part of your original code.

If you understand enough about your code, and the code in my edited post, it should be enough to piece together a complete solution.

And you could use the cmath library for complex numbers, but it's intended for doing calculations on known complex numbers. Such as taking the cosine of an imaginary number. It's not good for what you're trying to do here.

acwbrat · Oct 30th, 2007, 10:24 PM

I am going to try it out and then let you know if it works. Hopefully it will! Let me go check! Thanks Sane. But let me go check really quick.

acwbrat · Oct 30th, 2007, 10:32 PM

I tried running the program and it doesn't display my results at all. Also, when I tried performing calculations, the program would not run.

Oct 30th, 2007, 9:43 PM	#1
acwbrat Newbie Join Date: Oct 2007 Posts: 17 Rep Power: 0	Quadratic Formula in Python I have written a python code for quadratic formula . However, I need both real and complex numbers for my results. I have done research and noticed two differences: real numbers uses import math and complex numbers uses import cmath Here's my code. I would like to know what I have done wrong. I have even put my comments on there: (Toggle Plain Text) # quadraticcomplex.py # A program that computes the complex roots of a quadratic equation. # Illustrates use of the cmath library. # The presence of complex numbers also requires mathematical functions that can perform operations on them. # The imaginary component of a complex number is denoted by a suffix of ``J'' or ``j''; import cmath # Makes the cmath library available. def main(): # beginning of the code print "Hello! This program finds the complex solutions to a quadratic" print a, b, c = input("Please enter the coefficients (a, b, c): ") discRoot = cmath.sqrt(b * b - 4 * a * c) # formula solving discriminant root1 = (-b + discRoot) / (2 * a) # formula solving root1 root2 = (-b - discRoot) / (2 * a) # formula solving root2 print print "The solutions are:", root1, root2 # display the results main() # end of the code # quadraticcomplex.py # A program that computes the complex roots of a quadratic equation. # Illustrates use of the cmath library. # The presence of complex numbers also requires mathematical functions that can perform operations on them. # The imaginary component of a complex number is denoted by a suffix of ``J'' or ``j''; import cmath # Makes the cmath library available. def main(): # beginning of the code print "Hello! This program finds the complex solutions to a quadratic" print a, b, c = input("Please enter the coefficients (a, b, c): ") discRoot = cmath.sqrt(b * b - 4 * a * c) # formula solving discriminant root1 = (-b + discRoot) / (2 * a) # formula solving root1 root2 = (-b - discRoot) / (2 * a) # formula solving root2 print print "The solutions are:", root1, root2 # display the results main() # end of the code Last edited by DaWei; Oct 30th, 2007 at 10:26 PM. Reason: Added code tags. Read the rules.

Oct 30th, 2007, 9:49 PM	#2
Sane Programming Guru Join Date: Apr 2005 Location: Waterloo, Ontario Posts: 1,835 Rep Power: 5	Re: Quadratic Formula in Python Don't use cmath. Use math. Sorry about that. Edit: Just force it to be positive before you square root it, and then indicate that it's an imaginary number, calculating the real and imaginary portion how you normally would by hand. (Toggle Plain Text) disc = b*2 - 4ac # discriminant if disc < 0: disc = -disc # force it to be positive else: print "This quadratic does not have imaginary roots" return discRoot = math.sqrt(disc) root1r = (-b) / (2 a) # the real portion of root1 root1i = discRoot / (2 * a) # the imaginary portion of root1 root2r = root1r # the real portions are the same for each root root2i = -root1i # the only difference is it's negative disc = b*2 - 4ac # discriminant if disc < 0: disc = -disc # force it to be positive else: print "This quadratic does not have imaginary roots" return discRoot = math.sqrt(disc) root1r = (-b) / (2 a) # the real portion of root1 root1i = discRoot / (2 * a) # the imaginary portion of root1 root2r = root1r # the real portions are the same for each root root2i = -root1i # the only difference is it's negative So it's basically done how someone solving it with a pencil would do it. That's usually an ideal way of thinking about how to program a solution. By the way, wrap your code in [code][/code] tags next time. Last edited by Sane; Oct 30th, 2007 at 10:09 PM.

Oct 30th, 2007, 9:52 PM	#3
acwbrat Newbie Join Date: Oct 2007 Posts: 17 Rep Power: 0	Re: Quadratic Formula in Python Is this the same for real numbers too?

Oct 30th, 2007, 10:00 PM	#4
Sane Programming Guru Join Date: Apr 2005 Location: Waterloo, Ontario Posts: 1,835 Rep Power: 5	Re: Quadratic Formula in Python [Delete]

Oct 30th, 2007, 10:03 PM	#5
Sane Programming Guru Join Date: Apr 2005 Location: Waterloo, Ontario Posts: 1,835 Rep Power: 5	Re: Quadratic Formula in Python Sorry about that. I forgot that imaginary numbers are calculated in pieces when you use the quadratic formula. It's been too long. My first post is now edited. Last edited by Sane; Oct 30th, 2007 at 10:13 PM.

Oct 30th, 2007, 10:12 PM	#6
acwbrat Newbie Join Date: Oct 2007 Posts: 17 Rep Power: 0	Re: Quadratic Formula in Python Oh Thank you! Yes I am new to programming in python. I thought that the code was straight. But when I have noticed on import math, it would calculate the real numbers of the quadratic formula. I also thought that cmath would calculate complex numbers for quadratic formula. I thought in python, j represented complex numbers.

Oct 30th, 2007, 10:15 PM	#7
acwbrat Newbie Join Date: Oct 2007 Posts: 17 Rep Power: 0	Re: Quadratic Formula in Python So is this the correct format for the code? (Toggle Plain Text) def main(): # beginning of the code print "Hello! This program finds the complex solutions to a quadratic" print a, b, c = input("Please enter the coefficients (a, b, c): ") disc = b*2 - 4ac # discriminant if disc < 0: disc = -disc # force it to be positive else: print "This quadratic does not have imaginary roots" return discRoot = math.sqrt(disc) root1r = (-b) / (2 a) # the real portion of root1 root1i = discRoot / (2 * a) # the imaginary portion of root1 root2r = root1r # the real portions are the same for each root root2i = -root1i # the only difference is it's negative main() def main(): # beginning of the code print "Hello! This program finds the complex solutions to a quadratic" print a, b, c = input("Please enter the coefficients (a, b, c): ") disc = b*2 - 4ac # discriminant if disc < 0: disc = -disc # force it to be positive else: print "This quadratic does not have imaginary roots" return discRoot = math.sqrt(disc) root1r = (-b) / (2 a) # the real portion of root1 root1i = discRoot / (2 * a) # the imaginary portion of root1 root2r = root1r # the real portions are the same for each root root2i = -root1i # the only difference is it's negative main()

Oct 30th, 2007, 10:19 PM	#8
Sane Programming Guru Join Date: Apr 2005 Location: Waterloo, Ontario Posts: 1,835 Rep Power: 5	Re: Quadratic Formula in Python Yes, that should work, if you fix your indenting. And print out the output in a way the user can understand. If you want it to be able to handle both real and imaginary roots, you'll basically need to split the program up into two parts. If the discriminant is less than 0, you use the end part of the code I gave you. Otherwise, you make it use the end part of your original code. If you understand enough about your code, and the code in my edited post, it should be enough to piece together a complete solution. And you could use the cmath library for complex numbers, but it's intended for doing calculations on known complex numbers. Such as taking the cosine of an imaginary number. It's not good for what you're trying to do here.

Oct 30th, 2007, 10:24 PM	#9
acwbrat Newbie Join Date: Oct 2007 Posts: 17 Rep Power: 0	Re: Quadratic Formula in Python I am going to try it out and then let you know if it works. Hopefully it will! Let me go check! Thanks Sane. But let me go check really quick.

Oct 30th, 2007, 10:32 PM	#10
acwbrat Newbie Join Date: Oct 2007 Posts: 17 Rep Power: 0	Re: Quadratic Formula in Python I tried running the program and it doesn't display my results at all. Also, when I tried performing calculations, the program would not run.

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Programming Forums > Script Programming > Python

Quadratic Formula in Python