from sympy import *
from spb import *
x, k, a, b = symbols("x, k, a, b")
c = symbols("c", real=True)
f = exp(-x**2) * (Heaviside(x + a) - Heaviside(x - b))
fs = fourier_transform(f, x, k)
graphics(
    line_abs_arg_colored(fs, prange(k, -c, c),
        params={a: (1, -2, 2), b: (-2, -2, 2), c: (4, 0.5, 4)},
        label="Arg(fs)"),
    xlabel="k", yscale="log", ylim=(1e-03, 10))