conda create -n keras python=3.5 ipykernel
activate keras
python -m ipykernel install --user --name keras
jupyter notebook

使用这种方法安装的 Keras 才能被 Jupyter Notebook 调用。

I found the answer at http://ipython.readthedocs.io/en/stable/install/kernel_install.html#kernels-for-different-environments

ipykernel has to be linked to the environment, and then jupyter can use it.

The following installation procedure works:

conda create -n keras python=3.5 ipykernel
activate keras
python -m ipykernel install --user --name keras
jupyter notebook

Now if I call sys.executable in the jupyter notebook, it prints the correct environment from where the executables are accessed.