title: How to change Keras backend (where's the json file)?
body: <p>I have installed Keras, and wanted to switch the backend to Theano. I checked out <a href="https://stackoverflow.com/questions/40036748/keras-backend-importerror-cannot-import-name-ctc-ops">this post</a>, but still have no idea where to put the created json file. Also, below is the error I got when running <code>import keras</code> in Python Shell:</p>
  
  <blockquote>
    <p>Using TensorFlow backend.</p>
    
    <p>Traceback (most recent call last):   File "", line 1, in
    
        import keras   File "C:\Python27\lib\site-packages\keras__init__.py", line 2, in 
        from . import backend   File "C:\Python27\lib\site-packages\keras\backend__init__.py", line 64, in
    
        from .tensorflow_backend import *   File "C:\Python27\lib\site-packages\keras\backend\tensorflow_backend.py",
    line 1, in 
        import tensorflow as tf ImportError: No module named tensorflow</p>
  </blockquote>
  
  <p>When running <code>python -c "import keras; print(keras.__version__)"</code> from Windows command line, I got:</p>
  
  <blockquote>
    <p>Using TensorFlow backend. Traceback (most recent call last):   File
    "", line 1, in    File
    "C:\Python27\lib\site-packages\keras__init__.py", line 2, in 
        from . import backend   File "C:\Python27\lib\site-packages\keras\backend__init__.py", line 64, in
    
        from .tensorflow_backend import *   File "C:\Python27\lib\site-packages\keras\backend\tensorflow_backend.py",
    line 1, in 
        import tensorflow as tf ImportError: No module named tensorflow</p>
  </blockquote>
  
  <p>Can someone please help? Thanks!</p>