CODEWITHSUNDEEP
pythondictionarykey
Marcelle Guedes
Marcelle Guedes

Reputation: 1

Problems removing a value from a dictionary key

I have a dictionary in which each key has a certain amount of images saved. Like this:

key 1: [image1, image2, image3, image4]

After calculating the SSIM between each image of the key and the last image of the key: For example:

s1 = ssim(image4, image1)

If the value of s is bigger than a threshold, the image is kept in the dictionary.

key 1: [image1, image2, image3, image4]

If the value of s is less than a threshold, the image is deleted in the dictionary. Then:

key 1: [image2, image3, image4]

But in doing this I get the error:

IndexError: pop index out of range

Can anyone tell me what is wrong?

CODE

for img in range(len(img_dict1[key])):
    similarity=ssim(img_dict1[key][-1],img_dict1[key][img])
    if similarity > 0.85:
        continue
    else:
        img_dict1[key] = list(img_dict1[key]).pop(img)

Upvotes: 0

Views: 50

Answers (3)

Balaïtous
Balaïtous

Reputation: 896

You are modifing the img_dict1[key] list while you iterate its elements. So at the end of loop the list could be shorter than at begining. len(img_dict1[key]) is evaluated once, at the begining.

More pythonic is to build new list:

img_dict1[key] = [x for x in img_dict[key]
                  if ssim(img_dict1[key][-1], x) > 0.85]

Upvotes: 0

martineau
martineau

Reputation: 123393

You need to be careful about modifying the thing you are iterating over. To avoid that in this case you could use something called a list comprehension:

img_dict1[key] = [img_dict1[key][i] for i in range(len(img_dict1[key]))
                    if ssim(img_dict1[key][-1], img_dict1[key][i]) > 0.85]

This replaces the list with a new version that only has the elements in it you want.

Upvotes: 1

ARK1375
ARK1375

Reputation: 818

Do it like this:

for img in range(len(img_dict1[key])):
    similarity=ssim(img_dict1[key][-1],img_dict1[key][img])
    if similarity > 0.85:
        continue
    else:
        img_dict1[key].pop(img)

Explanation: pop automatically removes the element from the list/dictionary and modifies the list/dictionary on call. You only assign pop to a value if you want to use that value later. In your case, you don't need to assign it to anything.

Upvotes: 0

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