Error using cv2.findContours(), with python

Question

I've as of late began learning OpenCV on Python. 

I'm alluding to this instructional exercise here, to get some assistance on getting the forms of a picture. 

My code:

import cv2

import numpy as np

img = cv2.imread('shapes.jpg', 0)

img = cv2.medianBlur(img, 5)

thresh =     cv2.adaptiveThreshold(img,255,cv2.ADAPTIVE_THRESH_GAUSSIAN_C,\

cv2.THRESH_BINARY,11,2)

cv2.imshow('Thresh', thresh)

cv2.waitKey(0)

cv2.destroyAllWindows()

image, contours, hierarchy =   cv2.findContours(thresh.copy(),cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)

cv2.drawContours(image, countours, -1, (0,255,0), 3)

cv2.imshow('Contours', img)

cv2.waitKey(0)

cv2.destroyAllWindows()

The first thresholded picture is showing up, yet after that, I get a mistake message as

Traceback (most recent call last):

  File "contours.py", line 21, in <module>

    image, contours, hierarchy =     cv2.findContours(thresh.copy(),cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)

ValueError: need more than 2 values to unpack

Anyone, please me to resolve this issue.

Answer 1

You can use below code:

cv2.findContours(...)

just returns two objects, you're attempting to unload it into three. 

change that line to this:

contours, hierarchy =   cv2.findContours(thresh.copy(),cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)

It will work.

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