Error is not an Error?

[toml_12953]

When I enter the code blow, I check it and get no errors in the HPPL editor. When I try to run it, however, I get a syntax error in line 51. It works in CPython.

Traceback (most recent call last):
File "<stdin>", line 51
SyntaxError: invalid syntax

Code:

#PYTHON name
# cubic
from math import *

# compute real or complex roots of cubic polynomial
def cubic( a2, a1, a0 ):
    global z1,z2,z3
    Q = (3*a1 - a2**2)/9
    R = (9*a1*a2 - 27*a0 - 2*a2**3)/54
    D = Q**3 + R**2                        # polynomial discriminant

    if (D >= 0):                           # complex or duplicate roots

        S = sgn(R + sqrt(D))*abs(R + sqrt(D))**(1/3)
        T = sgn(R - sqrt(D))*abs(R - sqrt(D))**(1/3)

        z1 = -a2/3 + (S + T)               # real root
        z2 = -a2/3 - (S + T)/2             # real part of complex root
        z3 = -a2/3 - (S + T)/2             # real part of complex root
        im = abs(sqrt(3)*(S - T)/2)        # complex part of root pair

    else:                                  # distinct real roots

        th = acos(R/sqrt( -Q**3))
        
        z1 = 2*sqrt(-Q)*cos(th/3) - a2/3
        z2 = 2*sqrt(-Q)*cos((th + 2*pi)/3) - a2/3
        z3 = 2*sqrt(-Q)*cos((th + 4*pi)/3) - a2/3
        im = 0


    return im                               # imaginary part

# sign of number
def sgn( x ):
    if x < 0.0:
        return -1

    return 1


print("solve: x^3 + a*x^2 + b*x + c = 0")
a,b,c = input("a,b,c? ").split(",")

a=int(a)
b=int(b)
c=int(c)

im = cubic( a, b, c )

if im != 0.0:
    print("{",f"{z1:6.4f}, {z2:6.4f} + {im:6.4f}j, {z3:6.4f} - {im:6.4f}j","}")
else:
    print("{",f"{z1:6.4f}, {z2:6.4f}, {z3:6.4f}","}")
    
#end

EXPORT cubic()
BEGIN
  PYTHON(name);
END;