HTTP Methods – GET & POST

HTTP Methods

In this tutorial we will talk about HTTP methods. HTTP methods are the standard way of sending information to and from a web server. To break it down, a website runs on a server or multiple servers and simple returns information to a client (web-browser). Information is exchanged between the client and the server using an HTTP protocol that has a few different methods. We will be discussing the post commonly used ones called POST & GET.

GET

GET is the most commonly used HTTP method and it is typically used to retrieve information from a web server.

POST

POST is commonly used to send information to web server. It is more often used when uploading a file, getting form data and sending sensitive data. POST is a secure way to send data to a web server.

Creating a Form

For this example will create a form and discuss how we can use the POST HTTP method to send the information in our form to our server.

Here is a new html file I created called "login.html".

{% extends "base.html" %}
{% block title %}Login Page{% endblock %}

{% block content %}
<form action="#" method="post">
	<p>Name:</p>
	<p><input type="text" name="nm" /></p>
	<p><input type="submit" value="submit"/></p>
</form>
{% endblock %}

We've specified the method of the form to be post. Which means that when the form is submitted we will POST data to the web server in the form of a request.

Note the name of the text input field, we will use this to get it's value from our python code.

Back-End

What we're going to do is setup a login page that asks the user to type in their name. Once they hit the submit button they will be redirected to a page that displays the name they typed in.

We'll start by importing a new module called "request".

from flask import Flask, redirect, url_for, render_template, request

Next we'll setup the login page.

To specify that a page works with both POST and GET requests we need to add a method argument to the decorator.

@app.route("/login", methods=["POST", "GET"])

Now from inside the function we'll check if we are receiving a GET or POST request. We'll then define the operation to perform based on the request. If we have received a POST request that means we submitted the form and should redirect to the appropriate page. Otherwise we should simply return and render the login page.

def login():
    if request.method == "POST":
	user = request.form["nm"]
	return redirect(url_for("user", usr=user))
    else:
	return render_template("login.html")

Now we'll setup the user page. This will simply display the users name in h1 tags. Just for example/testing purposes, we don't need anything fancy.

@app.route("/<usr>")
def user(usr):
    return f"<h1>{usr}</h1>"

Now let's test out our site!

We'll head to the /login page and type our name. And after hitting submit! We get a page with our name on it...

Full Python Code

from flask import Flask, redirect, url_for, render_template, request

app = Flask(__name__)

@app.route("/")
def home():
    return render_template("index.html")

@app.route("/login", methods=["POST", "GET"])
def login():
    if request.method == "POST":
        user = request.form["nm"]
        return redirect(url_for("user", usr=user))
    else:
        return render_template("login.html")

@app.route("/<usr>")
def user(usr):
    return f"<h1>{usr}</h1>"

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