Keras Switch back end (Theano and TensorFlow)

The laboratory installed new Keras, found Keras default back end is TensorFlow, want to change back to Theano, see the official document also didn't understand, finally buttoned up, very simple.
Description of Chinese document: Keras Chinese document, switch back end

In fact, in C:\Users\75538 (75538 is my windos user name, to find your corresponding user name on the line) there is a folder. Keras, there are keras.json files, change the contents of the inside is good, if there is no folder and files, manually created on the line. with Theano words, Keras.json write

{
    "image_dim_ordering": "th", " 
    Epsilon": 1e-07, 
    "Floatx": "float32", 
    "backend": "Theano"
}

With thesorflow words, Keras.json write

{
    "image_dim_ordering": "TF", 
    "epsilon": 1e-07, 
    "Floatx": "float32", 
    "backend": "TensorFlow"
}

Finally, save it.