GET vs POST🔖

When your browser makes a request to a Flask route, it always uses an HTTP method. You've been using GET this whole time without thinking about it. POST is new.

What each one means🔖

GET — "Show me something." Used when you type a URL into the address bar, click a link, or load a page. The request is asking for a resource to display.

POST — "Here's some data." Used when you submit a form. The request is sending data to be processed — saved, recorded, acted on.

The difference isn't just technical convention. It reflects intent:

• /display with GET: "show me the tasks"
• /input with POST: "here is a new task to save"

One route, two behaviors🔖

Your /input route handles both. When a user visits /input in the browser, Flask runs the GET side and renders the blank form. When the user submits the form, Flask runs the POST side and saves the data.

@app.route("/input", methods=["GET", "POST"])
def input_task():
    if request.method == "POST":
        # User submitted the form — save the data
        ...
        return redirect(url_for("display"))
 
    # GET: render the blank form
    ...
    return render_template("input.html", projects=projects)

Three things to notice:

1. methods=["GET", "POST"] on the decorator — Flask blocks any method not listed. Omit this and submitting the form gives a 405 Method Not Allowed error.
2. if request.method == "POST" — the string is uppercase. This is where you handle the form submission.
3. The GET side is at the bottom — it runs when request.method is anything other than "POST".

What the form's method attribute does🔖

When you write <form method="POST">, you're telling the browser to send the form data as a POST request. If you omit method, the browser defaults to GET — and GET requests don't include form data in the request body, so request.form will be empty.

<form action="/input">