The suppression file that is shipped in Misc/valgrind-python.supp of the CPython 3(.x) source tarball only works with CPython 2.

This was tested on Debian Sid, with Python 3.4.3 and Python 2.7.9, both presumably not compiled with "--valgrind".

Since Debian does not ship valgrind-python.supp, I downloaded the source tarball for Python 3.4.3, and edited the suppression file (un-commenting the rules for Free and Realloc, as the documentation suggests for when running with a non-valgrind-aware version of CPython).

The test results are as follows:

$ uname -a
Linux mic 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt9-2 (2015-04-13) x86_64 GNU/Linux
$ lsb_release -a
No LSB modules are available.
Distributor ID:	Debian
Description:	Debian GNU/Linux unstable (sid)
Release:	unstable
Codename:	sid
$ valgrind --version
valgrind-3.10.1
$ python3 --version
Python 3.4.3
$ python2 --version
Python 2.7.9
$ valgrind --tool=memcheck --suppressions=/tmp/Python-3.4.3/Misc/valgrind-python.supp python3 -c 'import sys; print(sys.version)'
(...) ERROR SUMMARY: 666 errors from 61 contexts (suppressed: 0 from 0)
$ valgrind --tool=memcheck --suppressions=/tmp/Python-3.4.3/Misc/valgrind-python.supp python2 -c 'import sys; print(sys.version)'
(...) ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 486 from 28)

Note:

Additionally replacing

PyObject_Free -> _PyObject_Free

and

PyObject_Realloc -> _PyObject_Realloc

appears to fix the issue.

Thanks for the report.  This problem and solution was just reported recently in Issue24111.