bisection.py

#!/usr/bin/env python
import math
import sys 

CONST = -0.5307963268 

f1 = lambda x : x - 2 * math.sin(x)
f2 = lambda x : x * x * x - 25
f3 = lambda x : x * x * x + x - 4
f  = lambda x : CONST + math.asin(x) + x * math.sqrt(1-x * x)

def bis(a,b,n):
    for _ in range(n):
        c = (a+b)/2
        try:
            y1=f(a) # why? not used!
            y2=f(b)
            y3=f(c)
        except:
            print("The values must be in range bla bla")    
            sys.exit(1)
        if y1 * y2 > 0: #have same sign
            print(f'Root may be located outside the region [{a}, {b}]')
            sys.exit(1);
        if y1 * y2 == 0:
            print(a if y1 == 0 else b)
            sys.exit(1)
        if y3 > 0:
            b = c
        else:
            a = c
    print(c)
    

if __name__ == "__main__":
    if len(sys.argv) < 2:
        a = float(input('Enter a: '))
        b = float(input('Enter b: '))
        c = int(input('number of iterations: '))
    else:
        a = float(sys.argv[1])    
        b = float(sys.argv[2])    
        c = int(sys.argv[3])    
    bis(a,b,c)