Bisection method for finding root of f(x)

bisection_method.py

def main():
	A = 0; B = 12

	while True:
		C = (A + B) / 2

		val_a = evaluate_function(A)
		val_b = evaluate_function(B)
		val_c = evaluate_function(C)

		sign_a = determine_sign(val_a)
		sign_b = determine_sign(val_b)
		sign_c = determine_sign(val_c)

		# the machine used for the development could
		# only display up to x10^-15
		if (abs(A - B) <= (10**(-16))):
			break
		else:
			if sign_a == sign_c:
				A = C
			elif sign_b == sign_c:
				B = C
	
	print("\nBisection method\n\nValue of X[0] = 0, X[1] = 12\nRoot of f(x):", C, "\n")

def determine_sign(value):
	if value < 0:
		return 0 # we shall use 0 to denote negative
	elif value > 0:
		return 1 # we shall use 1 to denote positive
	else:
		return None

def evaluate_function(value):
	"Substitute A, B, C in the f(x)"
	return 3**(3 * value + 1) - 7 * 5**(2 * value)

main()