flask can't get post data from postman or web page,but work in python request

I use flask as API server. I test it with python it's ok!

class ModelLoader(MethodView):
    def __init__(self):
        pass

    def post(self):
        content = request.get_json()
        request
        X_input = content['X_input']
        X_in = str(X_input)
        pred_val,posib = predictor.predict(X_input=X_in)
        pred_val = pred_val.tolist()
        posib = str(round(posib,4)*100)
        #posib = posib.tolist()
        return jsonify({'pred_val': pred_val,'confident':posib})

    def initialize_models(json_path, weights_path, normalized_x, normalized_y):
        global predictor
        predictor = Predictor(json_path, weights_path, normalized_x, normalized_y)
        predictor.compile_model(loss='categorical_crossentropy', optimizer='adam')


    def run(host='0.0.0.0', port=19865):
        """Run a WSGI server using gevent."""
        app.add_url_rule('/predict', 
        view_func=ModelLoader.as_view('predict'))
        print('running server http://{0}'.format(host + ':' + str(port)))
        WSGIServer((host, port), app).serve_forever()

test code

import requests
def get_predictions(X_input):
    """Get predictions from a rest backend for your input."""
    print("Requesting prediction for XOR with {0}".format(X_input))
    r = requests.post("http://yansheng.wang:19865/predict", json={'input':  X_input})
print(r.status_code, r.reason)
resp = r.json()
prediction = resp['pred_val']
confident = resp['confident']
print("XOR of input: {0} is {1},on confident of {2} ".format(X_input, prediction,confident))

if __name__ == '__main__':

    X_inputs = ["885863343916543724"]

    for x_input in X_inputs:
        get_predictions(x_input)

when I run it I can't get post data from postman or web page!

the server console output difference is like below,what's wrong?:

45.76.182.34 - - [2017-07-29 12:11:55] "POST /predict HTTP/1.1" 200 162 0.044396
45.76.182.34 - - [2017-07-29 12:12:03] "POST /predict?input=3423432432424233 HTTP/1.1" 400 303 0.001046