Strange lines detected by openCV python -

i followed tutorial of python opencv, , trying use houghlinesp() detect lines, here code:

imgloc = '...\lines.jpg'  img = cv2.imread(imgloc) gray = cv2.cvtcolor(img, cv2.color_bgr2gray) edges = cv2.canny(gray, 50, 100) minlinelength = 20; maxlinegap = 5 lines = cv2.houghlinesp(edges, 1, np.pi/180, 100, \     minlinelength, maxlinegap) [[x1, y1, x2, y2]] in lines:     cv2.line(img, (x1, y1), (x2, y2), (0, 0, 255), 2) cv2.imshow('line', img) cv2.waitkey(); cv2.destroyallwindows() 

and here's get: apparently strange. there's many lines in sky never expected, , thought there more vertical lines on building, there's not.

the tutorial doesn't give pictures demonstrating how result should be, have no idea if that's normal or not.

so, is there problem in code lead wired image? if does, can make change let detect more vertical line?

==========update_1============

i followed comment's suggestion, more line can detected:

#minlinelength = 20; maxlinegap = 5 lines = cv2.houghlinesp(edges, 1, np.pi/180, 100, \     minlinelength = 10, maxlinegap = 5) 

still vertical lines lacked. , canny() result:

in result of canny() there vertical edges, why disappeared after houghlinesp()? (or that's visual error?)

==========update_2============

i added blur , value of minlinelength:

gray = cv2.gaussianblur(gray, (5, 5), 0) ... lines = cv2.houghlinesp(edges, 1, np.pi/180, 100, \         minlinelength = 50, maxlinegap = 5) 

the result clearer, still not vertical lines... , started wonder these slashes comes from

it might worth starting smoothing before performing canny edge detection.

i suggest higher values minlinelength (and maxlinegap, though should not large). should rid of smaller lines , connect vertical line segments detected. if still not bring out vertical lines, might have in threshold parameter.