Calling Julia function from a Python file

I need to integrate two files, one in python the other in julia. More precisely, I need to call a julia function, snapshot_sphere(b,h,data,m,r,d), from a python file. Moreover,I need to provide the parameters via the command line. I had difficulties in using PyJulia. For the moment an error message is persisting:

ModuleNotFoundError: No module named '_ctypes'

I found some dependencies related to libffi-dev. Installing it did not change anything. What should I do to call the julia function from the python file ?

Here is the code of the python file:

import argparse
from julia import Main  
from PIL import Image, ImageShow
parser = argparse.ArgumentParser(description="Projection of the picture")
parser.add_argument(
    "-f", 
    "--filename", 
    type=str, 
    action="store", 
    dest="fname",
    help="Name of the picture"
)
parser.add_argument(
    "-d", 
    "--density", 
    type=int, 
    action="store", 
    dest="density",
    help="Number samples per Pixel"
)
parser.add_argument(
    "-r", 
    "--radius", 
    type=float, 
    action="store", 
    dest="radius",
    help="Radius of the sphere"
)
parser.add_argument(
    "-x", 
    type=float, 
    action="store", 
    dest="x",
    help="X coordinate of the center"
)
parser.add_argument(
    "-y", 
    type=float, 
    action="store", 
    dest="y",
    help="Y coordinate of the center"
)
parser.add_argument(
    "-z",
    type=float, 
    action="store", 
    dest="z",
    help="Z coordinate of the center"
)


args = parser.parse_args()
print(args)
m = (args.x, args.y, args.z)
print(m)
im = Image.open(args.fname)
b, h = im.size

data = list(im.getdata())

Main.b = b
Main.h = h
Main.m = m
Main.r = args.radius
Main.d = args.density
Main.data = data
Main.include("projekt1.jl")
result = Main.eval("snapshot_sphere(b,h,data,m,r,d)")