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Slices at multiple intervals?

I have a file where I want to extract columns 2, 3, 4, 5 and column -4. These columns are not contiguous.

For clarity reasons, I would like to do something like

values = line.split()[columns_to_extract]

instead

values_part_one = line.split()[columns_to_extract_one] values_part_two = line.split()[columns_to_extract_two]

So I would like to make a slice that contains positions 2, 3, 4, 5 and -4 so that I can retrieve the values ​​in one line. Is it possible?

If not, are there any other neat oneliners out there that could do this?

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2 answers


Can a slice be made for this? Not.

However, all is not lost! You can use operator.itemgetter

:

getter = operator.itemgetter(2, 3, 4, 5, -4)


Example:

>>> import operator
>>> getter = operator.itemgetter(2, 3, 4, 5, -4)
>>> getter(range(50))  # Note, returns a `tuple`
(2, 3, 4, 5, 46)
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parts = line.split()
values_part_one = [parts[i] for i in columns_to_extract_one]
values_part_two = [parts[i] for i in columns_to_extract_two]

or as @mgilson points out, you can use operator.itemgetter

to get tuples:



import operator
extract_one = operator.itemgetter(*columns_to_extract_one) # or list explicitly
extract_two = operator.itemgetter(*columns_to_extract_two) # if using fixed cols

parts = line.split()
values_part_one = extract_one(parts)
values_part_Two = extract_two(parts)

Note that both of these will fail IndexError

if the item you are trying to retrieve is not large enough to contain all of the specified indices.

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