With the prebuilt version of tensorflow, I did: virtualenv --system-site-packages ~/tensorflow
and somehow got it working with keras. Now I've compiled tensorflow in another shell/directory, where to start with I did: virtualenv --system-site-packages . and I got it running with keras on my net, with a nice speedup. Then I went back to my previous shell, did a deactivate, then virtualenv --system-site-packages ~/tf_compile/tensorflow to point to the dir that was '.' above, but my prompt path did not pick up '(tensorflow)' as before: % virtualenv --system-site-packages ~/tf_compile/tensorflow New python executable in /Users/priot/tf_compile/tensorflow/bin/python Installing setuptools, pip, wheel...done. priot keras% and I get: % python prog.py ... File "/Users/ppp/anaconda/lib/python2.7/site- packages/keras/backend/tensorflow_backend.py", line 1, in <module> import tensorflow as tf ImportError: No module named tensorflow Seems inconsistent. % virtualenv --version 15.1.0 % python --version Python 2.7.10 :: Anaconda custom (x86_64) OS: OSx Darwin -- https://mail.python.org/mailman/listinfo/python-list