Python3 Flask-缺少1个必需的位置参数：“ self”

Question

I have very simple python code to access Amazon Simple Queue Service. But I get

   builtins.TypeError
TypeError: get_queue() missing 1 required positional argument: 'self'

My code:

class CloudQueue(object):

    conn = boto.sqs.connect_to_region("eu-west-1",
        aws_access_key_id="abc",
        aws_secret_access_key="abc")


    @app.route('/get/<name>')  
    def get_queue(self, name):

        if(name != None):
            queue = self.conn.get_queue(str(name)) <--------- HERE
        return conn.get_all_queues()


if __name__ == "__main__":
    cq = CloudQueue()
    app.debug = True
    app.run()

Answer 1

You cannot register methods as routes; at the time the decorator runs the class is still being defined and all you registered is the unbound function object. Since it is not bound to an instance there is no self to pass in.

Do not use a class here; create the connection anew for each request:

@app.route('/get/<name>')  
def get_queue(name):
    conn = boto.sqs.connect_to_region("eu-west-1",
        aws_access_key_id="abc",
        aws_secret_access_key="abc")

    queue = conn.get_queue(name)
    return 'some response string'

You could set it as a global but then you need to make sure you re-create the connection on the first request (so it continues to work even when using a WSGI server using child processes to handle requests):

@app.before_first_request()
def connect_to_boto():
    global conn
    conn = boto.sqs.connect_to_region("eu-west-1",
        aws_access_key_id="abc",
        aws_secret_access_key="abc")

@app.route('/get/<name>')  
def get_queue(name):
    queue = conn.get_queue(name)
    return 'some response string'

Use this only if you are sure that boto connection objects are thread-safe.