Do you want to loop randomly through every item in huge sequence without outputting the same item twice? Would you like to do this while keeping minimal state? Then you need a Linear Congruential Generator iterator!
from lcgit import lcg
from ipaddress import ip_network
for i in lcg(ip_network("10.0.0.0/8")):
print(i)The code above, will print out each of the 16,777,216 IPs in the 10.0.0.0/8
network in random order. Which is useful. But what would be more useful is
if you can output some now, save your state, and do some more later!
This is where emit comes in. Creating an lcg with emit=True will cause
the iterator to emit its state along with the sequence value. If you save
this state, and pass it back to a new lcg it will produce iterators that will
continue the random sequence where you left off.
from lcgit import lcg
from ipaddress import ip_network
my_lcg = lcg(ip_network("192.168.1.0/24"), emit=True)
it = iter(my_lcg)
# print the first 32 random values
for i in range(32):
value, state = next(it)
print(value)
# save state, and come back later
save_it(state, to_something)How large is the state? Am I going to need a flag bit for each item? Will I
need to buy more RAM and disk? How about a tuple of four integers, no matter
how large the sequence is!? The state variable at the end of the code block
above would be storing something very similar to: (149, 223, 161, 32)
To continue the generator where we left off, you simply create a new one for
the same sequence, and pass in your stored state:
restored = load_it(from_somewhere) # (149, 223, 161, 32)
my_new_lcg = lcg(ip_network("192.168.1.0/24"), state=restored)
# print the remaining values
for i in my_new_lcg:
print(i)lcgit doesn't just work with networks. It will also work with any of the
Python sequence types.
for i in lcg(range(100_000_000_000_000)):
print(i)We welcome contributions! Please see CONTRIBUTING.md for
details.
This project is in the worldwide public domain.
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