问题
This question already has an answer here:
- How to create a GUID/UUID in Python 7 answers
I need to generate a unique ID based on a random value.
回答1:
Perhaps uuid.uuid4() might do the job. See uuid for more information.
回答2:
You might want Python's UUID functions:
21.15. uuid — UUID objects according to RFC 4122
eg:
import uuid
print uuid.uuid4()
7d529dd4-548b-4258-aa8e-23e34dc8d43d
回答3:
unique and random are mutually exclusive. perhaps you want this?
import random
def uniqueid():
seed = random.getrandbits(32)
while True:
yield seed
seed += 1
Usage:
unique_sequence = uniqueid()
id1 = next(unique_sequence)
id2 = next(unique_sequence)
id3 = next(unique_sequence)
ids = list(itertools.islice(unique_sequence, 1000))
no two returned id is the same (Unique) and this is based on a randomized seed value
回答4:
Maybe this work for u
str(uuid.uuid4().fields[-1])[:5]
回答5:
import time
import random
import socket
import hashlib
def guid( *args ):
"""
Generates a universally unique ID.
Any arguments only create more randomness.
"""
t = long( time.time() * 1000 )
r = long( random.random()*100000000000000000L )
try:
a = socket.gethostbyname( socket.gethostname() )
except:
# if we can't get a network address, just imagine one
a = random.random()*100000000000000000L
data = str(t)+' '+str(r)+' '+str(a)+' '+str(args)
data = hashlib.md5(data).hexdigest()
return data
回答6:
Maybe the uuid module?
回答7:
here you can find an implementation :
def __uniqueid__():
"""
generate unique id with length 17 to 21.
ensure uniqueness even with daylight savings events (clocks adjusted one-hour backward).
if you generate 1 million ids per second during 100 years, you will generate
2*25 (approx sec per year) * 10**6 (1 million id per sec) * 100 (years) = 5 * 10**9 unique ids.
with 17 digits (radix 16) id, you can represent 16**17 = 295147905179352825856 ids (around 2.9 * 10**20).
In fact, as we need far less than that, we agree that the format used to represent id (seed + timestamp reversed)
do not cover all numbers that could be represented with 35 digits (radix 16).
if you generate 1 million id per second with this algorithm, it will increase the seed by less than 2**12 per hour
so if a DST occurs and backward one hour, we need to ensure to generate unique id for twice times for the same period.
the seed must be at least 1 to 2**13 range. if we want to ensure uniqueness for two hours (100% contingency), we need
a seed for 1 to 2**14 range. that's what we have with this algorithm. You have to increment seed_range_bits if you
move your machine by airplane to another time zone or if you have a glucky wallet and use a computer that can generate
more than 1 million ids per second.
one word about predictability : This algorithm is absolutely NOT designed to generate unpredictable unique id.
you can add a sha-1 or sha-256 digest step at the end of this algorithm but you will loose uniqueness and enter to collision probability world.
hash algorithms ensure that for same id generated here, you will have the same hash but for two differents id (a pair of ids), it is
possible to have the same hash with a very little probability. You would certainly take an option on a bijective function that maps
35 digits (or more) number to 35 digits (or more) number based on cipher block and secret key. read paper on breaking PRNG algorithms
in order to be convinced that problems could occur as soon as you use random library :)
1 million id per second ?... on a Intel(R) Core(TM)2 CPU 6400 @ 2.13GHz, you get :
>>> timeit.timeit(uniqueid,number=40000)
1.0114529132843018
an average of 40000 id/second
"""
mynow=datetime.now
sft=datetime.strftime
# store old datetime each time in order to check if we generate during same microsecond (glucky wallet !)
# or if daylight savings event occurs (when clocks are adjusted backward) [rarely detected at this level]
old_time=mynow() # fake init - on very speed machine it could increase your seed to seed + 1... but we have our contingency :)
# manage seed
seed_range_bits=14 # max range for seed
seed_max_value=2**seed_range_bits - 1 # seed could not exceed 2**nbbits - 1
# get random seed
seed=random.getrandbits(seed_range_bits)
current_seed=str(seed)
# producing new ids
while True:
# get current time
current_time=mynow()
if current_time <= old_time:
# previous id generated in the same microsecond or Daylight saving time event occurs (when clocks are adjusted backward)
seed = max(1,(seed + 1) % seed_max_value)
current_seed=str(seed)
# generate new id (concatenate seed and timestamp as numbers)
#newid=hex(int(''.join([sft(current_time,'%f%S%M%H%d%m%Y'),current_seed])))[2:-1]
newid=int(''.join([sft(current_time,'%f%S%M%H%d%m%Y'),current_seed]))
# save current time
old_time=current_time
# return a new id
yield newid
""" you get a new id for each call of uniqueid() """
uniqueid=__uniqueid__().next
import unittest
class UniqueIdTest(unittest.TestCase):
def testGen(self):
for _ in range(3):
m=[uniqueid() for _ in range(10)]
self.assertEqual(len(m),len(set(m)),"duplicates found !")
hope it helps !
回答8:
This will work very quickly but will not generate random values but monotonously increasing ones (for a given thread).
import threading
_uid = threading.local()
def genuid():
if getattr(_uid, "uid", None) is None:
_uid.tid = threading.current_thread().ident
_uid.uid = 0
_uid.uid += 1
return (_uid.tid, _uid.uid)
It is thread safe and working with tuples may have benefit as opposed to strings (shorter if anything). If you do not need thread safety feel free remove the threading bits (in stead of threading.local, use object() and remove tid altogether).
Hope that helps.
回答9:
import time
def new_id():
time.sleep(0.000001)
return time.time()
On my system, time.time() seems to offer 6 significant figures after the decimal point. With a brief sleep it should be guaranteed unique with at least a moderate amount of randomness down in the last two or three digits.
You could hash it as well if you're worried.
来源：https://stackoverflow.com/questions/1210458/how-can-i-generate-a-unique-id-in-python