How to Find Out If Python Is Compiled with Ucs-2 or Ucs-4

How to find out if Python is compiled with UCS-2 or UCS-4?

When built with --enable-unicode=ucs4:

>>> import sys
>>> print sys.maxunicode
1114111

When built with --enable-unicode=ucs2:

>>> import sys
>>> print sys.maxunicode
65535

How to change python from UCS2 to UCS4

Use:

./configure --enable-unicode=ucs4

to configure the source to build with UCS4 support.

From the ./configure --help output:

  --enable-unicode[=ucs[24]]
                          Enable Unicode strings (default is ucs2)

Build Python as UCS-4 via pyenv

Installing python with pyenv with ucs2:

$ export PYTHON_CONFIGURE_OPTS=--enable-unicode=ucs2
$ pyenv install -v 2.7.11
  ...
$ pyenv local 2.7.11
$ pyenv versions
  system
* 2.7.11 (set by /home/nwani/.python-version)
$ /home/nwani/.pyenv/shims/python
Python 2.7.11 (default, Aug 13 2016, 13:42:13) 
[GCC 4.8.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sysconfig
>>> sysconfig.get_config_vars()['CONFIG_ARGS']
"'--prefix=/home/nwani/.pyenv/versions/2.7.11' '--enable-unicode=ucs2' '--libdir=/home/nwani/.pyenv/versions/2.7.11/lib' 'LDFLAGS=-L/home/nwani/.pyenv/versions/2.7.11/lib ' 'CPPFLAGS=-I/home/nwani/.pyenv/versions/2.7.11/include '"

Installing python with pyenv with ucs4:

$ pyenv uninstall 2.7.11
pyenv: remove /home/nwani/.pyenv/versions/2.7.11? y
$ export PYTHON_CONFIGURE_OPTS=--enable-unicode=ucs4
$ pyenv install -v 2.7.11
...
$ pyenv local 2.7.11
$ pyenv versions
  system
* 2.7.11 (set by /home/nwani/.python-version)
$ /home/nwani/.pyenv/shims/python
Python 2.7.11 (default, Aug 13 2016, 13:49:09) 
[GCC 4.8.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sysconfig
>>> sysconfig.get_config_vars()['CONFIG_ARGS']
"'--prefix=/home/nwani/.pyenv/versions/2.7.11' '--enable-unicode=ucs4' '--libdir=/home/nwani/.pyenv/versions/2.7.11/lib' 'LDFLAGS=-L/home/nwani/.pyenv/versions/2.7.11/lib ' 'CPPFLAGS=-I/home/nwani/.pyenv/versions/2.7.11/include '"

How to recompile Python2.7 with 4-byte unicode enabled?

From the output of

./configure --help

the correct option is given as

--enable-unicode=ucs4

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