summary about http.request, GET and POST, form, and route in flask

1. Request

HTTP works as a request-response protocol between a client and server. To access incoming request data, you can use the global request object. Flask parses incoming request data for you and gives you access to it through that global object. Internally Flask makes sure that you always get the correct data for the active thread if you are in a multithreaded environment. Some examples of how to get request data: request.form, request.args.get, request.files.

2. GET and POST

POST: The browser tells the server that it wants to post some new information to that URL and that the server must ensure the data is stored and only stored once. This is how HTML forms usually transmit data to the server.

PUT: Similar to POST but the server might trigger the store procedure multiple times by overwriting the old values more than once. Now you might be asking why this is useful, but there are some good reasons to do it this way. Consider that the connection is lost during transmission: in this situation a system between the browser and the server might receive the request safely a second time without breaking things. With POST that would not be possible because it must only be triggered once.

3. form

The form tag needs two attributes set:

3.1. form action

action is where the data is sent. If action is omitted, it assumed to be the current page (the same URL). In flask, action is the URL that the form data is sent to on submit. Generate it with url_for. It can be omitted if the same URL handles showing the form and processing the data.

Add a view to handle the form data:

@app.route('/handle_data', methods=['POST'])
def handle_data():
    projectpath = request.form['projectFilepath']
    # your code
    # return a response

Set the form's action to that view's URL:

<form action="{{ url_for('handle_data') }}" method="post">
    <input type="text" name="projectFilepath">
    <input type="submit">
</form>

3.2. form method

method: Whether to submit the data as a query string (GET) or form data (POST).

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