Right now uuid4 can be implemented one of 3 ways:- If there's a libuuid (and it's not OS X's) it uses that.- Fallback to os.urandom- If that raises an exception, fall back to the random moduleI propose to simplify this to _just_ use os.urandom always. Reasons:- Its security properties are more obviously correct. (There's a large comment in uuid.py about how libuuid doees the wrong thing with fork on OS X, who knows if it's correct on other platforms)- It's simpler.- It's faster:a_gaynor@miranda:~$ python -mtimeit -s "import uuid; import os; import ctypes" "_buffer = ctypes.create_string_buffer(16); uuid._uuid_generate_random(_buffer); bytes(_buffer.raw)"100000 loops, best of 3: 10 usec per loopa_gaynor@miranda:~$ python -mtimeit -s "import uuid; import os; import ctypes" "_buffer = ctypes.create_string_buffer(16); uuid._uuid_generate_random(_buffer); bytes(_buffer.raw)"100000 loops, best of 3: 10.3 usec per loopa_gaynor@miranda:~$ python -mtimeit -s "import uuid; import os; import ctypes" "_buffer = ctypes.create_string_buffer(16); uuid._uuid_generate_random(_buffer); bytes(_buffer.raw)"100000 loops, best of 3: 9.99 usec per loopa_gaynor@miranda:~$ python -mtimeit -s "import uuid; import os; import ctypes" "_buffer = ctypes.create_string_buffer(16); uuid._uuid_generate_random(_buffer); bytes(_buffer.raw)"100000 loops, best of 3: 10.2 usec per loopa_gaynor@miranda:~$ python -mtimeit -s "import uuid; import os; import ctypes" "_buffer = ctypes.create_string_buffer(16); uuid._uuid_generate_random(_buffer); bytes(_buffer.raw)"100000 loops, best of 3: 10.2 usec per loopa_gaynor@miranda:~$a_gaynor@miranda:~$a_gaynor@miranda:~$a_gaynor@miranda:~$a_gaynor@miranda:~$ python -mtimeit -s "import uuid; import os; import ctypes" "os.urandom(16)"100000 loops, best of 3: 8.94 usec per loopa_gaynor@miranda:~$ python -mtimeit -s "import uuid; import os; import ctypes" "os.urandom(16)"100000 loops, best of 3: 8.92 usec per loopa_gaynor@miranda:~$ python -mtimeit -s "import uuid; import os; import ctypes" "os.urandom(16)"100000 loops, best of 3: 8.97 usec per loopa_gaynor@miranda:~$ python -mtimeit -s "import uuid; import os; import ctypes" "os.urandom(16)"100000 loops, best of 3: 8.93 usec per loopa_gaynor@miranda:~$ python -mtimeit -s "import uuid; import os; import ctypes" "os.urandom(16)"100000 loops, best of 3: 8.94 usec per loopa_gaynor@miranda:~$a_gaynor@miranda:~$a_gaynor@miranda:~$ python --versionPython 2.7.3

(Note that the speed difference would be even bigger on a recent python, 2.7.3 was before the file descriptor was cached for os.urandom)

On Oct 29, 2015, at 10:30 PM, Alex Gaynor wrote:>Right now uuid4 can be implemented one of 3 ways:If you're hacking on the uuid module, keep in mindissue22807

This looks like a good idea to me, faster and more secure seems like a total win.

New changeset24bdc4940e81 by Benjamin Peterson in branch '2.7':always use os.urandom for the uuid4 algorithm (closes#25515)https://hg.python.org/cpython/rev/24bdc4940e81New changeset70be1f9c9255 by Benjamin Peterson in branch '3.5':always use os.urandom for the uuid4 algorithm (closes#25515)https://hg.python.org/cpython/rev/70be1f9c9255New changeset756d040aa8e8 by Benjamin Peterson in branch 'default':merge 3.5 (#25515)https://hg.python.org/cpython/rev/756d040aa8e8