ValueError: too many values to unpack in cv2.findContours

[TheMatt2]

For whatever reason, cv2.findContours on line 211 returns three arguments instead of the expected 2. From playing with it, I found that by eliminating the first value would solve the problem.
I am not knowledgeable about cv2 so if this is something obvious someone please say so. (MacOS, cv2 '3.2.0').
Here is the fix that worked for me.
result = cv2.findContours(edges.copy(), cv2.RETR_TREE, cv2.CHAIN_APPROX_NONE)
contours, hierarchy = result if len(result) == 2 else result[1:3]

[ossiach]

Adding a third value in front of the other two also solved the problem for me.
For example:
_, contours, hierarchy = cv2.findContours(edges.copy(), cv2.RETR_TREE, cv2.CHAIN_APPROX_NONE)

Apparently findContours got changed some time ago:
https://stackoverflow.com/questions/25504964/opencv-python-valueerror-too-many-values-to-unpack

[bhosalems]

Yes above solution worked for me too.

[amar74]

conts,h=cv2.findContours(maskFinal.copy(),cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE)
ValueError: too many values to unpack (expected 2)

sir please tell me where I'm wrong

[pallavipundir]

Just initialize with one more variable in front of other two on L.H.S.For example:-
_,conts,h=cv2.findContours(maskFinal.copy(),cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE)

I've used _(Underscore) here.You can give any name or simply use it as underscore only.

[plusminuschirag]

Is it safe to say that find Contours needs three variables to store the returned value?

[pallavipundir]

Ofcourse it is.Don't worry, it is safe to say this.

[vrajchauhan0]

(cnts, _) = cv2.findContours(closed.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

Not able to understand. Please help me. giving error too many values to unpack.

[pallavipundir]

Use like this:-
(_, cnts, h)= cv2.findContours(closed.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

[pallavipundir]

Because you cannot unpack 3 values from the tuple and place them in a tuple of two,which you are doing.

[lmiller1990]

What is the third value, though? According to the docs, only two should be returned. https://docs.opencv.org/2.4/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html#findcontours

Edit: I am using opencv3, cannot find the docs for findContours in 3.0 though, only 2.4.

[bharath5673]

EASY FIX ;)

( _ , cnts , _ ) = cv2.findContours(threshFrame.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
ValueError: not enough values to unpack (expected 3, got 2)

try this

( cnts , _ )

python is right.
you cannot unpack 3 values from the turple and place them in a turple of two ###

happy coding ;)

[rutujar]

@bharath5673 this works ,thank u

[Sanjeeth8733]

I'm getting the same error unable to resolve it.

in extract_bv(image)
22 ret,f6 = cv2.threshold(f5,15,255,cv2.THRESH_BINARY)
23 mask = np.ones(f5.shape[:2], dtype="uint8") * 255
---> 24 image, contours, hierarchy = cv2.findContours(f6.copy() ,cv2.RETR_LIST ,cv2.CHAIN_APPROX_SIMPLE)
25 for cnt in contours:
26 if cv2.contourArea(cnt) <= 200:

ValueError: not enough values to unpack (expected 3, got 2)