Python

Debug me please

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Join Date: Oct 2009

Posts: 19

Reputation: simpatar is an unknown quantity at this point

Solved Threads: 0

simpatar

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Newbie Poster

Debug me please

Oct 24th, 2009

Alright, this is how my newest program looks like:

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import math
 
def main():
    print('This program finds the real solutions to a quadratic')
    print
 
    s = float(input('Please enter the coefficients (a,b,c): '))
    a, b, c = s.split(',')
 
 
    discRoot = float(math.sqrt(b * b - 4 * a * c))
    root1 = (-b + discRoot) / (2*a)
    root2 = (-b - discRoot) / (2*a)
 
    print
    print('The solutions are:', root1, ('and'), root2)
 
main()
import math

def main():
    print('This program finds the real solutions to a quadratic')
    print

    s = float(input('Please enter the coefficients (a,b,c): '))
    a, b, c = s.split(',')

    
    discRoot = float(math.sqrt(b * b - 4 * a * c))
    root1 = (-b + discRoot) / (2*a)
    root2 = (-b - discRoot) / (2*a)

    print
    print('The solutions are:', root1, ('and'), root2)

main()

and i get this error msg:
in main
in main
s = float(input('Please enter the coefficients (a,b,c): '))
ValueError: invalid literal for float(): 2, 3, -2

Help ._.

Last edited by simpatar; Oct 24th, 2009 at 9:53 am.

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Join Date: Oct 2004

Posts: 4,109

Reputation: vegaseat is just really nice

Solved Threads: 943

vegaseat

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DaniWeb's Hypocrite

Oct 24th, 2009

I assume you are using Python3?

When you are splitting the input string you still get strings, so each coefficients (a,b,c) has to be converted to a float before you apply it to your formula.

May 'the Google' be with you!

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Join Date: Oct 2009

Posts: 19

Reputation: simpatar is an unknown quantity at this point

Solved Threads: 0

simpatar

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Newbie Poster

Oct 24th, 2009

Correct, I use python3.

I deleted the float infront of the input since it was causing the program to bug. But shouldnt I be able to tell python to make all variables that i put in the input to be floats? if not,
how do I make them float nicely?

Last edited by simpatar; Oct 24th, 2009 at 10:28 am.

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Join Date: Jul 2008

Posts: 1,067

Reputation: jlm699 is a jewel in the rough

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jlm699

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Knows where his Towel is

Oct 24th, 2009

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Originally Posted by simpatar

Correct, I use python3.

I deleted the float infront of the input since it was causing the program to bug. But shouldnt I be able to tell python to make all variables that i put in the input to be floats? if not,
how do I make them float nicely?

Basically you have to iterate over your "split" coefficients and then perform float conversion on each one independently. When you split them they return a list, which you'll be doing your iteration on. Here's the steps broken down:

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>>> my_coeffs = input('Enter coefficients (a,b,c): ')
Enter coefficients (a,b,c): 3, 5.5, 4.25
>>> coeff_list = my_coeffs.split(',')
>>> coeff_list
['3', ' 5.5', ' 4.25']
>>> # Create an empty list to store our float values
>>> float_list = []
>>> # Iterate over our string coefficients
>>> for each in coeff_list:
...     # turn each one into a float
...     conv_coeff = float(each)
...     # and finally store it
...     float_list.append(conv_coeff)
...     
>>> float_list
[3.0, 5.5, 4.25]
>>>
>>> my_coeffs = input('Enter coefficients (a,b,c): ')
Enter coefficients (a,b,c): 3, 5.5, 4.25
>>> coeff_list = my_coeffs.split(',')
>>> coeff_list
['3', ' 5.5', ' 4.25']
>>> # Create an empty list to store our float values
>>> float_list = []
>>> # Iterate over our string coefficients
>>> for each in coeff_list:
...     # turn each one into a float
...     conv_coeff = float(each)
...     # and finally store it
...     float_list.append(conv_coeff)
...     
>>> float_list
[3.0, 5.5, 4.25]
>>>

But thankfully in python you can make it look a little more beautiful than the above using list comprehension:

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 python Syntax (Toggle Plain Text) 
>>> my_coeffs = raw_input('Enter coefficients (a,b,c): ')
Enter coefficients (a,b,c): 2, 4.5, 5.25
>>> float_list = [float(each) for each in my_coeffs.split(',')]
>>> float_list
[2.0, 4.5, 5.25]
>>>
>>> my_coeffs = raw_input('Enter coefficients (a,b,c): ')
Enter coefficients (a,b,c): 2, 4.5, 5.25
>>> float_list = [float(each) for each in my_coeffs.split(',')]
>>> float_list
[2.0, 4.5, 5.25]
>>>

List comprehension allows us to create a list from another iterable while performing some action (and there's even room for logic). This is a powerful tool that you would probably benefit from learning.

Here's the documentation about it

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Join Date: Oct 2004

Posts: 4,109

Reputation: vegaseat is just really nice

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vegaseat

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DaniWeb's Hypocrite

Oct 24th, 2009

Just modify your code, also take care of negative numbers in your square root ...

 Help with Code Tags 
 python Syntax (Toggle Plain Text) 
import math
 
def main():
    print('This program finds the real solutions to a quadratic')
    print()
 
    s = input('Please enter the coefficients (a,b,c): ')
    a, b, c = s.split(',')
    a = float(a)
    b = float(b)
    c = float(c)
 
    disc = b * b - 4 * a * c
    if disc < 0:
        print("root will give imaginary number")
        return
    discRoot = math.sqrt(disc)
    root1 = (-b + discRoot) / (2*a)
    root2 = (-b - discRoot) / (2*a)
 
    print()
    print('The solutions are:', root1, ('and'), root2)
 
main()
import math

def main():
    print('This program finds the real solutions to a quadratic')
    print()

    s = input('Please enter the coefficients (a,b,c): ')
    a, b, c = s.split(',')
    a = float(a)
    b = float(b)
    c = float(c)

    disc = b * b - 4 * a * c
    if disc < 0:
        print("root will give imaginary number")
        return
    discRoot = math.sqrt(disc)
    root1 = (-b + discRoot) / (2*a)
    root2 = (-b - discRoot) / (2*a)

    print()
    print('The solutions are:', root1, ('and'), root2)

main()