GUID.py
Revision as of 16:06, 19 July 2009 by PeterHarding (talk | contribs)
globally unique identifier made up of time and ip
# Copyright (C) 2002 Dr. Conan C. Albrecht
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
import random
import socket
import time
class GUID:
'''A globally-unique identifier made up of time and ip and 3 random digits: 35 characters wide
A globally unique identifier that combines ip, time, and random bits. Since the
time is listed first, you can sort records by guid. You can also extract the time
and ip if needed.
GUIDs make wonderful database keys. They require no access to the
database (to get the max index number), they are extremely unique, and they sort
automatically by time. GUIDs prevent key clashes when merging
two databases together, combining data, or generating keys in distributed
systems.
'''
rand = random.Random()
ip = ''
try:
ip = socket.gethostbyname(socket.gethostname())
except (socket.gaierror): # if we don't have an ip, default to someting in the 10.x.x.x private range
ip = '10'
for i in range(3):
ip += '.' + str(rand.randrange(1, 254))
hexip = ''.join(["%04x" % long(i) for i in ip.split('.')]) # leave space for ip v6 (65K in each sub)
lastguid = ''
def __init__(self, guid=None):
'''Constructor. Use no args if you want the guid generated (this is the normal method)
or send a string-typed guid to generate it from the string'''
if guid is None:
self.guid = self.__class__.lastguid
while self.guid == self.__class__.lastguid:
# time part
now = long(time.time() * 1000)
self.guid = ("%016x" % now) + self.__class__.hexip
# random part
self.guid += ("%03x" % (self.__class__.rand.randrange(0, 4095)))
self.__class__.lastguid = self.guid
elif type(guid) == type(self): # if a GUID object, copy its value
self.guid = str(guid)
else: # if a string, just save its value
assert self._check(guid), guid + " is not a valid GUID!"
self.guid = guid
def __eq__(self, other):
'''Return true if both GUID strings are equal'''
if isinstance(other, self.__class__):
return str(self) == str(other)
return 0
def __str__(self):
'''Returns the string value of this guid'''
return self.guid
def time(self):
'''Extracts the time portion out of the guid and returns the
number of milliseconds since the epoch'''
return long(self.guid[0:16], 16)
def ip(self):
'''Extracts the ip portion out of the guid and returns it
as a string like 10.10.10.10'''
# there's probably a more elegant way to do this
ip = []
index = 16
while index Here's a possibly improved version with basic GUID format checking, __eq__ implementation and a more pythonic ip implementation. Hope you like it.
thanks for sharing.
#!/usr/bin/python
# A globally unique identifier made up of time and ip
# Copyright (C) 2002 Dr. Conan C. Albrecht
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
import random
import socket
import time
class GUID:
'''A globally-unique identifier made up of time and ip and 3 random digits: 35 characters wide
A globally unique identifier that combines ip, time, and random bits. Since the
time is listed first, you can sort records by guid. You can also extract the time
and ip if needed.
GUIDs make wonderful database keys. They require no access to the
database (to get the max index number), they are extremely unique, and they sort
automatically by time. GUIDs prevent key clashes when merging
two databases together, combining data, or generating keys in distributed
systems.
'''
rand = random.Random()
ip = ''
try:
ip = socket.gethostbyname(socket.gethostname())
except (socket.gaierror): # if we don't have an ip, default to someting in the 10.x.x.x private range
ip = '10'
for i in range(3):
ip += '.' + str(rand.randrange(1, 254))
hexip = ''.join(["%04x" % long(i) for i in ip.split('.')]) # leave space for ip v6 (65K in each sub)
lastguid = ''
def __init__(self, guid=None):
'''Constructor. Use no args if you want the guid generated (this is the normal method)
or send a string-typed guid to generate it from the string'''
if guid is None:
self.guid = self.__class__.lastguid
while self.guid == self.__class__.lastguid:
# time part
now = long(time.time() * 1000)
self.guid = ("%016x" % now) + self.__class__.hexip
# random part
self.guid += ("%03x" % (self.__class__.rand.randrange(0, 4095)))
self.__class__.lastguid = self.guid
elif type(guid) == type(self): # if a GUID object, copy its value
self.guid = str(guid)
else: # if a string, just save its value
assert self._check(guid), guid + " is not a valid GUID!"
self.guid = guid
def __eq__(self, other):
'''Return true if both GUID strings are equal'''
if isinstance(other, self.__class__):
return str(self) == str(other)
return 0
def __str__(self):
'''Returns the string value of this guid'''
return self.guid
def time(self):
'''Extracts the time portion out of the guid and returns the
number of milliseconds since the epoch'''
return long(self.guid[0:16], 16)
def ip(self):
'''Extracts the ip portion out of the guid and returns it
as a string like 10.10.10.10'''
# there's probably a more elegant way to do this
ip = []
index = 16
while index