python - subtracting ranges from bigger ranges

问题

The problem I have is that I basically would like to find if there are any free subnets between a BGP aggregate-address (ex: 10.76.32.0 255.255.240.0) and all the network commands on the same router (ex: 10.76.32.0 255.255.255.0, 10.76.33.0 255.255.255.0)

In the above example 10.76.34.0 -> 10.76.47.255 would be free.

I'm thinking of tackling this problem by converting the IP addresses and subnet masks to binary and subtracting that way.

To keep it simple I will keep this example in decimal but doing this would leave me with the following problem: let's say I have a range from 1 to 250, I subtract from this a smaller range that goes from 20 to 23, I would like to end up with a range from 1 to 19 and 24 to 250.

Using the range command doesn't really give me the expected results and while I could possibly create a list with every item in the range and subtract another list with a sub-set of items, it seems to me that it might not be a good idea to have lists with possibly tens of thousands of elements.

Hunor

回答1:

If you are trying to create a "range" with a gap in it, i.e., with 1-9 and 24-250, you could try to use filterfalse (or ifilterfalse if you are using Python 2.X) from the itertools module, which takes as its arguments a predicate and a sequence, and returns elements of the sequence where the predicate returns False. As an example, if you do:

from itertools import filterfalse
new_range = filterfalse(lambda x: 20 <= x <= 23, range(1,251))

new_range will be an iterable containing the numbers 1-19, and 24-250, which can be used similarly to range():

for i in new_range:
    do_things()

回答2:

The question has been asked long ago but I want to add numpy array answer.

import numpy as np
aa=np.arange(1,251)
bb=np.concatenate((np.array(aa[aa<20]),np.array(aa[aa>23])))
print(bb)

output

array([  1,   2,   3,   4,   5,   6,   7,   8,   9,  10,  11,  12,  13,
        14,  15,  16,  17,  18,  19,  24,  25,  26,  27,  28,  29,  30,
        31,  32,  33,  34,  35,  36,  37,  38,  39,  40,  41,  42,  43,
        44,  45,  46,  47,  48,  49,  50,  51,  52,  53,  54,  55,  56,
        57,  58,  59,  60,  61,  62,  63,  64,  65,  66,  67,  68,  69,
        70,  71,  72,  73,  74,  75,  76,  77,  78,  79,  80,  81,  82,
        83,  84,  85,  86,  87,  88,  89,  90,  91,  92,  93,  94,  95,
        96,  97,  98,  99, 100, 101, 102, 103, 104, 105, 106, 107, 108,
       109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121,
       122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134,
       135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147,
       148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160,
       161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173,
       174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186,
       187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199,
       200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212,
       213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225,
       226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238,
       239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250])

来源：https://stackoverflow.com/questions/40043103/python-subtracting-ranges-from-bigger-ranges

标签

python

networking

range

subnet