Dexters - 7 months ago 12

Python Question

The following are two arrays:

`import difflib`

import scipy

import numpy

a1=numpy.array(['198.129.254.73','134.55.221.58','134.55.219.121','134.55.41.41','198.124.252.101'], dtype='|S15')

b1=numpy.array(['198.124.252.102','134.55.41.41','134.55.219.121','134.55.219.137','134.55.220.45', '198.124.252.130'],dtype='|S15')

difflib.get_close_matches(a1[-1],b1,2)

output:

`['198.124.252.130', '198.124.252.102']`

shouldnt

`'198.124.252.102'`

`'198.124.252.101'`

I looked at the documentation where they have specified about some floating type weights but no information on algorithm use.

I am in need to find if the absolute difference between the last two octet is 1 (provided the first three octets are same).

So I am finding the closest string first and then checking that closest string for the above condition.

Is there any other function or way to achieve this? Also how does

`get_close_matches()`

`ipaddr`

Answer

Well, there is this part in the docs explaining your issue:

This does not yield minimal edit sequences, but does tend to yield matches that “look right” to people.

For getting the results you are expecting you could use the Levenshtein_distance.

But for comparing IPs I would suggest to use integer comparison:

```
>>> parts = [int(s) for s in '198.124.252.130'.split('.')]
>>> parts2 = [int(s) for s in '198.124.252.101'.split('.')]
>>> from operator import sub
>>> diff = sum(d * 10**(3-pos) for pos,d in enumerate(map(sub, parts, parts2)))
>>> diff
29
```

You can use this style to create a compare function:

```
from functools import partial
from operator import sub
def compare_ips(base, ip1, ip2):
base = [int(s) for s in base.split('.')]
parts1 = (int(s) for s in ip1.split('.'))
parts2 = (int(s) for s in ip2.split('.'))
test1 = sum(abs(d * 10**(3-pos)) for pos,d in enumerate(map(sub, base, parts1)))
test2 = sum(abs(d * 10**(3-pos)) for pos,d in enumerate(map(sub, base, parts2)))
return cmp(test1, test2)
base = '198.124.252.101'
test_list = ['198.124.252.102','134.55.41.41','134.55.219.121',
'134.55.219.137','134.55.220.45', '198.124.252.130']
sorted(test_list, cmp=partial(compare_ips, base))
# yields:
# ['198.124.252.102', '198.124.252.130', '134.55.219.121', '134.55.219.137',
# '134.55.220.45', '134.55.41.41']
```