Problems in traversing contours in python using OpenCV library

I am designing an algorithm in which I have to traverse through every contour in an image and apply a condition on it. I am using OpenCV library to do this. And the code is as follows:

i=0
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
ret,thresh = cv2.threshold(gray,1,255,0)
contours,hierarchy=cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
while contours:
if (cv2.contourArea(contours[i]) < 5000 and cv2.arcLength(contours[i],True) < 200 ):
    cv2.drawContours(img,contours,i,(0,255,0),3)
i = i+1
contours = contours.h_next()

The error is:

Traceback (most recent call last):
File "C:UsersNOOR BRARDocumentsCollege Stuff5th SEMe-yantratask1PS1_Task1Task1_Practicetest_imagescountourImagemine.py", line 55, in <module>
contours = contours.h_next()
AttributeError: 'list' object has no attribute 'h_next'

Answer

I have never used h_next but whenever I’ve iterated over contours

for cnt in contours:
    if (cv2.contourArea(cnt) < 5000 and cv2.arcLength(cnt, True) < 200 ):
        cv2.drawContours(img, [cnt], -1, (0,255,0), 3)

has worked.

It appears that you’re mixing the iterator n_next with [i]…try the following

while contours:
    if (cv2.contourArea(contours) < 5000 and cv2.arcLength(contours, True) < 200 ):
        cv2.drawContours(img, [contours], -1, (0,255,0), 3)
    i = i+1
    contours = contours.h_next()