bisection method for continuous functions

from math import log2, ceil, exp


def tested_function(x):
    return exp(x) - 4*x


if __name__ == '__main__':
    print('[x0, x1]')
    pivot = 0
    x0 = float(input('x0 = '))
    x1 = float(input('x1 = '))
    if int(input('precision(1) or iteration(2) ?')) == 1:
        precision = int(input('Precision ?'))
        iteration = ceil(log2(pow(10, precision) * (x1 - x0)/2))
    else:
        iteration = int(input('Iteration ?'))
        precision = ceil((x1 - x0) / pow(2, iteration))
    precision = str(precision)
    for i in range(iteration):
        x2 = (x0 + x1) / 2
        r = tested_function(x2)
        print('{}'.format(r))
        if r == pivot:
            print('done')
            break
        elif (tested_function(x0) > pivot > r) or \
                (tested_function(x0) < pivot < r):
            x1 = x2
        else:
            x0 = x2
        print('[{}, {}]'.format(x0, x1))
        print('{}'.format((x0 + x1) / 2))
    print('iteration : {}'.format(iteration))
    print('precision : {}'.format(precision))