I use list comprehension to load only the images from a folder that meet a certain condition.
In the same operation, I would also like to keep track of those that do not meet the condition. This is where I am having trouble.
If the if and else conditions are at the beginning, each iteration yields a resulting element. The items that are caught by else are replaced by None rather than being excluded from the result list.
I can’t figure out how to add an else condition such that an operation can be done on the items caught by else without including them in the resulting list.
here is a simplified and generalized version of the code:
exclude_imgs = [1, 3]
final = [
n
for ix, n in enumerate(sorted(["img1", "img4", "img3", "img5", "img2"]))
if ix + 1 not in exclude_imgs
]
[ins] In [4]: final
Out[4]: ['img2', 'img4', 'img5']
adding else condition to store excluded images:
exclude_imgs = [1, 3]
excluded = []
final = [
n if ix + 1 not in exclude_imgs else excluded.append(n)
for ix, n in enumerate(sorted(["img1", "img4", "img3", "img5", "img2"]))
]
[ins] In [6]: final
Out[6]: [None, 'img2', None, 'img4', 'img5']
[ins] In [7]: excluded
Out[7]: ['img1', 'img3']
How can I write this so that the results are as follows:
final: ['img2', 'img4', 'img5']
excluded: ['img1', 'img3']
?
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2
exclude_imgs = [1, 3]
# convert all element of exclude_imgs into string
exclude_imgs = [str(x) for x in exclude_imgs]
# declare the list of images into a variable so that it is easy to call later. No need to sort
img_lst = ["img1", "img4", "img3", "img5", "img2"]
excluded = []
final = []
# No need to sort
for x in img_lst:
# This condition checks if any of exclude_imgs is present in the image.
if any(y in x for y in exclude_imgs):
excluded.append(x)
else:
final.append(x)
print(excluded) # Output: ['img1', 'img3']
print(final) # Output: ['img4', 'img5', 'img2']
Consider not using a list comprehension at all, precisely because you want to create two lists, not just one.
exclude_imgs = [1, 3]
excluded = []
final = []
for ix, n in enumerate(sorted(["img1", "img4", "img3", "img5", "img2"]), start=1):
(excluded if ix in excluded_imgs else final).append(n)