C implementation of Python 2 threading's Lock, RLock, and Condition

pip install cthreading==0.3



cthreading implements Python 2 Lock, RLock, and Condition in C, speeding up threads synchronization and decreasing cpu usage.

Status: Travis-CI Build Status


cthreading eliminates the overhead of threading.RLock and threading.Condition which are implemented in pure Python in Python 2. In particular, threading.Condition is implemented using polling. In Python 3 threading.Condition is implemented without polling; cthreading implements a similar design in C.

$ time python whispers.py -m cthreading
real    0m2.664s
user    0m2.965s
sys     0m0.808s

$ time python3 whispers.py
real    0m9.664s
user    0m8.949s
sys     0m1.812s

$ time python whispers.py
real    0m14.914s
user    0m16.986s
sys     0m12.690s

$ time python whispers.py -m pthreading
real    0m20.169s
user    0m23.062s
sys     0m17.022s

Your application is unlikely to have similar workload; do not expect this improvement.

For more info see https://github.com/nirs/cthreading/wiki/performance.


Import cthreading before any other module and monkeypatch the thread and threading modules. From this point, threading.Lock, threading.RLock, and threading.Condition are using cthreading.

import cthreading

Note: cthreading will raise RuntimeError if the threading module was imported before cthreading.monkeypatch() is called.

Tested platforms


  • Fedora 22 / Python 2.7.10
  • RHEL 7.2 / Python 2.7.5
  • RHEL 7.2 / Python 2.7.10+ (upstream)
  • RHEL 7.1 / Python 2.7.5
  • RHEL 6.7 / Python-2.6.6
  • Ubuntu 14.04 Server / Python 2.7.6
  • Ubuntu 12.04 Server / Python 2.7.3 (python regression tests not available)
  • Ubuntu 12.04 / Python 2.6.9 (Travis container)
  • Ubuntu 12.04 / Python 2.7.9 (Travis container)


  • RHEL 7.2 / Python 2.7.5
  • RHEL 7.2 / Python 2.7.10+ (upstream)


For rpm based distributions:

yum install python-devel python-test

For deb based distributions:

apt-get install python-dev libpython2.7-testsuite

Installing Python packages:

pip install pytest pytest-timeout yappi==0.93

Building and running the quick tests:


Before submitting patches, run the Python regression tests suite:

make regrtest

Check the Makefile for more info.

Similar projects

  • pthreading - uses pthread_mutex and pthread_cond apis directly via ctypes. This introduces undefined behavior and actually slower and increases cpu usage in most cases compared to the original Python implementation.