I understand this may be an old question, but still I cannot find solution from off-the-shelf Q$A. Here is the problem:
I am following Udacity \"Mac
More than likely either Tensorflow is not installed in the right Python environment of Conda or not installed at all. Follow the below steps:
$ conda create -n tensorflow python=3.5
Once that is done, need to activate that as below:
$ source activate tensorflow
Then when you open IPython Notebook or Spyder, it will recognize the Tensorflow.