sets and subsets

[Bart Nessux]

Peter Otten wrote:
> Bart Nessux wrote:
> 
> 
>>By using lists, I can create sets of number. Suppose I have three lists.
>>One list is the super-set, one is a set that contains all the numbers
>>(just like the super-set) and the last is sub-set of the super-set. For
>>example:
>>
>>a = [1,2,3,4,5]       # The super-set.
>>b = [1,2,3,4,5] # Looks just like the super-set, but it's not.
>>c = [2,4]     # A sub-set
>>
>>I'd like to remove 2 & 4 from set b BECAUSE they are present in set c...
>>this would make the sets look like this:
>>
>>a = [1,2,3,4,5]
>>b = [1,3,5]
>>c = [2,4]
>>
>>How do I test set c to find what it contains and then look at set b to
>>see if it contains any of those same numbers, and if so, remove them.
> 
> 
> You want set operations, so why would you use lists?

All my data are in lists:

inputFile = file('ips.txt', 'r')	#Super-set
include = inputFile.readlines()
inputFile.close()

# The file below is compiled manually by hand... add IPs to it
# whenever you want to exclude them from IP_protection.
readFile = file('excluded_ips.txt', 'r')	#Sub-set to exclude
exclude = readFile.readlines()
readFile.close()

include = [x for x in include if x not in exclude]	#Magic of Elaine

outputFile = file('pruned_ips.txt' , 'w')
for i in include:
    print>> outputFile, i,
outputFile.close()