when running the following script, we found python2 comsume a lot memory while python3 does not have the issue.

import re
import time
NON_PRINTABLE = re.compile(u'[^\U00010000-\U0010ffff]')
time.sleep( 30 )

python2:
  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND                            
 6943 root      20   0  109956  93436   3956 S   0.0   1.2   0:00.30 python

python3:
  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND                            
 6952 root      20   0   28032   8880   4868 S   0.0   0.1   0:00.02 python3

Hi, I tracked it down and found that this problem was introduced in python2.7.9 by following commit:

https://hg.python.org/cpython/rev/ebd48b4f650d

We usually do not backport optimizations to 2.7. It could be backported if a regression was introduced in one of 2.7 bugfixes, but range() was here before ebd48b4f650d.

Also, range(0x10000,0x10ffff+1) takes only 32*2**16 = 2 MiB of memory. It is small in comparison with total memory consumption. Obviously there are other causes of the difference between 2.7 and 3.x.

> but range() was here before ebd48b4f650d.

before ebd48b4f650d, _optimize_unicode use xrange. So python2.7.8 is ok and python2.7.9 consume much memory in my test case.

> Obviously there are other causes of the difference between 2.7 and 3.x.

Maybe it is because my python was compiled with --enable-unicode=ucs4.

As mentioned on the attached PR, Python 2.7 has reached EOL and this can no longer be accepted.  Thanks for the report and patch anyway!