secant.py

from math import *

# INPUT PARAMATERS:
eqn_str = input("equation for y=f(x) > ")
a = float(input("lower limit (a) > "))
b = float(input("upper limit (b) > "))
tolerance = float(input("tolerance value > "))
max_iterations = float(input("maximum number of iterations > "))

fx = eval("lambda x: " + eqn_str)  # function representing our equation
line = f"{'':-^3}|{'':-^22}|{'':-^22}|{'':-^22}|{'':-^21}"

# print table headers:
print(line)
print(f"{'n':^2} | {'a':^20} | {'b':^20} | {'c':^20} | {'|(c) - (c*)| < e':^20}")
print(line)

n = 1  		# iteration number
fa = fx(a)  # function at a
fb = fx(b)  # function at b

while n <= max_iterations:
    # calculate c
    c = ((a * fb) - (b * fa)) / (fb - fa)
    fc = fx(c)
    err = abs(c - b)  # estimated absolute error

    # print a row in table
    print(f"{n:^2} | {a:^20} | {b:^20} | {c:^20} | {err:^20.10f} ")

    if fc == 0 or err < tolerance:  # solution is found?
        break

    # update next interval:
    a = b
    b = c
    fa = fb
    fb = fc
    n = n + 1
else:
    print("Method failed after maximum iterations")
print(line)