HTTP Request and Response with Flask

3 min readSep 23, 2021

What is HTTP?

HTTP (Hypertext Transfer Protocol) is communication protocol between client and server. In web development, we basically should know HTTP request and response.

HTTP request and response

HTTP request is client request to server. HTTP response is sever response back to client. For example, if you type url in web browser and enter, browser create http request containing http method, request url, request headers and request body and send it to web browser through the internet. Server get those request and make http response containing http status code, http header and http body and response back to browser. Finally browser show the result.

Form request
Catch HTTP request with flask request object
Flask Response

Quick Start

create a folder
in folder create main.py
create templates folder(jinja template) and create login.html and success.html

main.py

from flask import Flask, request, render_template, redirect, url_forapp = Flask(__name__)
app.config['ENV'] = 'development'# creating route
@app.route("/")
def login():
    return render_template("login.html")@app.route("/success")
def success():
    return "this is success"if __name__ == "__main__":
    app.run(debug=True)

Form request

HTML login form

<div class="form_container">
    <form class="form_2" method="POST" action={{url_for("login")}}>
    <div class="input_fields">
        <h1>User Login</h1>
        <input type="text" name="email" id="name" placeholder="Name" required>
        <input type="password" name="password" id="password" placeholder="Password" required>
    </div>
    <button type="submit" class="outline_md_btn">
        Submit
    </button>
    </form>
</div>

Flask Request Object

from flask import request

1. Get request method

Client requested HTTP method. There are five main HTTP methods.

GET
POST
PATCH
PUT
DELETE

Catch client requested method with

request.method

main.py

from flask import request@app.route("/", methods=['GET', 'POST'])
def login():
     print(request.method)
     return render_template("login.html")

In login route, allow both ‘GET’ request and ‘POST’ request.

If ‘GET’ request, return render login.html (jinja template)

If ‘POST’ request, get form data and redirect to success page

@app.route("/", methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        print(request.form['email'])
        print(request.form['password'])
        return redirect(url_for("success"))
    return render_template("login.html")

More about HTTP method and use in API.

2. Get form data

request.form[' ']

form request (login.html)

<input type="text" name="email" id="name" placeholder="Name" required>

get form email input data (main.py)

request.form['email']

3. Get Request Header

request.headers

request.headers will show the header of HTTP request. User login or sometime request can be passed with user data in headers and we can check like this.

@app.route("/", methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        print(request.headers)        
        print(request.form['email'])
        print(request.form['password'])
        return redirect(url_for("success"))
    return render_template("login.html")

4. Get files from request

request.files['upload']

5. Get cookies from request

request.cookies.get('auth_token')

6. Get request arguments

Url ➜ http://127.0.0.1:5000/success?email=xawyk%40mailinator.com

@app.route("/success")
def success():
    print(request.args['email'])
    return render_template("success.html")

you can also pass from login route(main.py)

@app.route("/", methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        print(request.headers)
        print(request.form['email'])
        print(request.form['password'])
        return redirect(url_for("success", email=request.form['email']))
    return render_template("login.html")


@app.route("/success")
def success():
    print(request.args['email'])
    return f"<h1>{request.args['email']}</h1>"

Flask Response

RETURN value automatically response with response status code and json data (jsonify) or text or html templates.

return template

@app.route("/", methods=['GET', 'POST'])
def login():
    return render_template("login.html")

return text

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

return json

@app.route("/users")
def user():
    return jsonify({'name': 'sofia', 'email': 'sofia@gmail.com'})

Make response

If you want to modify response data, you can use make_response() as response.

response = make_response(render_template('home.html'))
response.set_cookie('auth_token', encoded_jwt.decode())
return response, 201

More about flask