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Very new to Python - bliengme - Sep-24-2020
This was copied from a book but gives several errors. Help!
from math import exp
def bisection(f,a,b,tol= 1e-3):
if f(a)*f(b) > 0:
print(f"No roots or more than one root in [{a},{b}]")
return
m = (a+b)/2
while abs(f(m)) > tol:
if f(a)*f(m) < 0:
b = m
else:
a = m
m = (a+b)/2
return m
#call the method for f(x)= x**2-4*x+exp(-x)
f = lambda x: x**2-4*x+exp(-x)
sol = bisection(f,-0.5,1,1e-6)
print(f"x = {sol:g} is an approximate root, f({sol:g}) = {f(sol):g}")
RE: Very new to Python - snippsat - Sep-24-2020
(Sep-24-2020, 12:36 PM)bliengme Wrote: This was copied from a book but gives several errors. HelpYou should post error(Traceback) you get,How to ask Smart Questions.
The problem here is that indentation is mess upped,have to be carful when copy from book/pdf then this can happen.
Here is a fix,indentation in Python is always 4-space.
from math import exp
def bisection(f,a,b,tol= 1e-3):
if f(a)*f(b) > 0:
print(f"No roots or more than one root in [{a},{b}]")
return
m = (a+b)/2
while abs(f(m)) > tol:
if f(a)*f(m) < 0:
b = m
else:
a = m
m = (a+b)/2
return m
#call the method for f(x)= x**2-4*x+exp(-x)
f = lambda x: x**2-4*x+exp(-x)
sol = bisection(f,-0.5,1,1e-6)
print(f"x = {sol:g} is an approximate root, f({sol:g}) = {f(sol):g}")Output:x = 0.25 is an approximate root, f(0.25) = -0.158699RE: Very new to Python - bliengme - Sep-25-2020
many thanks