Trying To Make Loop For A Function That Stops After The Result Is Lower Than A Certain Value

I'm taking a beginner python class and part of an exercise we were given was this: The point x with the property x= sin(x)−ax+ 30 is called a fixed point of the function f(x) =

Solution 1:

To see what happens during the iteration, I advise adding print(i, x) to the loop in either the original code (after being corrected with the needed indent) or your code. You can remove it before submitting.

The original and your code lack from math import sin. Code posted should be ready to run, including needed imports.

Your posted code neglects to define y=200, but there is no need to add that for the problem as specified. In any case, for i in range(y) will give i the values 0, 1, ..., 199. Your condition i > 200 will never be true. The easiest way to do something if the loop does not break is to use an else: clause. Or you can replace iterations with the more descripting failure and correct your condition.

Combined with Tom K's comment, possible code that works is

from math import sin

x = 0.5
a = 0.5for i in range(200):
    x1 = sin(x) - a*x + 30print(i, x)  # remove before submitting
    ifabs(x1 - x) < 1.e-8:
        break
    x = x1
else:
    print('The condition was not met within 200 iteration steps.')

print('The result after {num} iterations is {res}.'.format(num=i, res=x))

This prints for a = .5 and 8:

The result after 59 iterations is20.649274368307022.

The condition was not met within200 iteration steps.
The result after 199 iterations is-1.1949487767945635e+181.