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Remove specific elements from list with a pattern
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Remove specific elements from list with a pattern
#1
#Hi everyone, here is my problem:

# My Printer-Software got an error while selecting the double printing feature
# My initial goal was to print 4 pages on each side of the printing paper
#(4 in the front and 4 in the back)

#I need a list that follows this Pattern:
#[1, 2, 3, 4, 9, 10, 11, 12, 17, 18, 19, 20, 25, 26, 27, 28] (for the front pages)
#[5, 6, 7, 8, 13, 14, 15, 16, 21, 22, 23, 24, 29, 30, 31, 32] (for the back pages)

# I need to expand this list to 8000 but with a decent code...

input = 8000
output = list(range(input + 1))
del output[0]

print(output)

#Here I am stuck because this list follows this order [1, 2, 3, 4,...]. How can I change it to the desired list structure like above?
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#2
Try the following:
>>> N = 9
>>> sum([list(range(i, j)) for i, j in zip([4*k+1 for k in range(N)][1::2], [4*k + 5 for k in range(N)][1::2])], [])
[5, 6, 7, 8, 13, 14, 15, 16, 21, 22, 23, 24, 29, 30, 31, 32]
>>> sum([list(range(i, j)) for i, j in zip([4*k+1 for k in range(N)][0::2], [4*k + 5 for k in range(N)][0::2])], [])
[1, 2, 3, 4, 9, 10, 11, 12, 17, 18, 19, 20, 25, 26, 27, 28, 33, 34, 35, 36]
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#3
Maybe not the most standard way, but I would use compress and cycle here to create two iterators for the front and the back.  

from itertools import cycle, compress

n = 32
front = compress(range(1,n+1), cycle([1]*4 + [0]*4))
rear = compress(range(1,n+1), cycle([0]*4 + [1]*4))

print(f"front: {list(front)}")
print(f"rear: {list(rear)}")
Output:
front: [1, 2, 3, 4, 9, 10, 11, 12, 17, 18, 19, 20, 25, 26, 27, 28] rear: [5, 6, 7, 8, 13, 14, 15, 16, 21, 22, 23, 24, 29, 30, 31, 32]
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#4
(Oct-11-2020, 01:30 AM)bowlofred Wrote: Maybe not the most standard way, but I would use compress and cycle here to create two iterators for the front and the back.  

from itertools import cycle, compress

n = 32
front = compress(range(1,n+1), cycle([1]*4 + [0]*4))
rear = compress(range(1,n+1), cycle([0]*4 + [1]*4))

print(f"front: {list(front)}")
print(f"rear: {list(rear)}")
Output:
front: [1, 2, 3, 4, 9, 10, 11, 12, 17, 18, 19, 20, 25, 26, 27, 28] rear: [5, 6, 7, 8, 13, 14, 15, 16, 21, 22, 23, 24, 29, 30, 31, 32]

an elegant way. thank you!!!
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