hough_line_2.py

import cv2
import numpy as np

img = cv2.imread('sudoku.png')
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
edges = cv2.Canny(gray, 50, 150, apertureSize=3)
cv2.imshow('edges', edges)
lines = cv2.HoughLinesP(edges, 1, np.pi / 180, 100, minLineLength= 100, maxLineGap = 10)

for line in lines:

    x1, y1, x2, y2 = line[0]

    cv2.line(img, (x1, y1), (x2, y2), (0, 0, 255), 2)

cv2.imshow('image', img)
k = cv2.waitKey(0)
cv2.destroyAllWindows()