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pythonbisection

Calling a bisection method root finiding function and calingit to solve any function in python

I have written a general bisection method to find roots of the provided function, I want to call it to solve a quadratic function. here's my generalroot.py

# generalroot.py
# determines the root of any general function

def root_bisection(f, a, b, tolerance=1.0e-6):
    dx = abs(b-a)
    while dx > tolerance:
        x = (a+b)/2.0

        if (f(a)*f(x)) < 0:
            b = x
        else:
            a = x
        dx = abs(b-a)
    return

Now I am calling it to solve a quadratic function 

from math import *
from generalroot import *

def function(y):
    y = y**2 + 5*x - 9
    return y

func = root_bisection(y, 0, 1)

print  'Found f(x) =0 at x = %0.8f +/- %0.8f' % ( func , tolerance)

and am getting the following error:

raceback (most recent call last):
  File "quadfrombisectionroot.py", line 8, in <module>
    func = root_bisection ( y , 0, 1)
NameError: name 'y' is not defined

Please help me fix the error, thanks

Solution

  • root_bisection is expecting a function as its first argument. You should probably call it like that:

    func = root_bisection(function, 0, 1)

    Also you are having a typo in the definition of function. Replace x with y.

    As a general piece of advice: Never do from libraryXYZ import * but only import the functions you really need. This makes the code much more readable.