- 16 Kas 2022
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Hello everyone, I am Suppressor. Today, I will introduce you to Flask, a micro web framework of Python.
Flask is a simple and lightweight micro web framework used for web development and web applications under the Python programming language. The reason it's called a "micro" web framework is due to its minimal and lightweight structure. Flask provides developers with only the essential tools and can be extended with various libraries when more complex features are needed.
Flask URL Structure and Routing
Looking at the basic structure and routing of Flask, in the simplest explanation, a request is sent from our computer to our application, and the response to the request is displayed in our browser. When we start a Flask application, it also sets up a server at a local address and we continue our operations from there. Flask automatically determines this address and shows it to us when we start the application.
Routing and Syntax
Syntax:
- Task: app.route
- Define Function: def route():
- Task: return "Hello"
Generally, the syntax is like this:
Python:
from flask import Flask
app = Flask([B]name[/B])
@app.route("/")def route():return "Hello"
if [B]name[/B] == "[B]main[/B]":app.run()Adding the Flask library to the program and creating a Flask object:
Python:
from flask import Flask
app = Flask([B]name[/B])Next, we tell Flask which function to run when a certain event occurs using the "route" decorator (decorators are special functions in Python):
Python:
@app.route("/")def route():return "Hello"At this point, when we go to the root directory, meaning the main URL, we will get a response like "Hello".
Another example is from the /admin directory.
Templates
Templates are structures that exist to interpret languages like HTML, CSS, JS in your browser and display them to the user. As you saw above, we could only place string expressions on the screen. However, using templates, we can have our HTML, CSS, and JavaScript codes interpreted by the browser. Before moving on to the coding phase, we need to create a folder named "templates" in the directory where our Flask application is located. By default, Flask pulls the templates it will interpret from this folder. Then, I create a file named "index.html" inside it. Additionally, you need to include render_template in the library part. You can see it in the code below.
Python:
from flask import Flask, render_template
app = Flask([B]name[/B])
@app.route("/template")def index():return render_template('index.html')
if [B]name[/B] == "[B]main[/B]":app.run(debug=True)If we want to show an HTML file to the user, we use the render_template() function and write the name of the HTML file we want from the "templates" folder.
Example HTML Code:
Example HTML Code:
HTML:
<!DOCTYPE html>
<html lang="tr"><head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Arge Team</title> <script src="https://cdn.tailwindcss.com"></script></head><body><style> body { background-color: black; text-align: center; font-style: italic; } h6 { color: rgb(220 38 38); } p { color: rgb(132 204 22); }</style> <p>Flask</p> <br> <h6>Template</h6></body></html>Sending Data from Flask Application to HTML File
Jinja Syntax
Conditional Statements and Loops
For loops, conditional statements, etc.:
For showing variables:
We learned above how to display the index file to the user. But what if we need to send data from a Flask application we wrote to the user? Let's first look at how to do this.
Again, write the codes I wrote above and similarly write render_template('index.html'). But this time, there's a difference: you can write any name you want, but you need to give one parameter. The name doesn't matter; I gave the parameter name "sayı".
You can define this in the upper lines or directly here:
For loops, conditional statements, etc.:
For showing variables:
We learned above how to display the index file to the user. But what if we need to send data from a Flask application we wrote to the user? Let's first look at how to do this.
Again, write the codes I wrote above and similarly write render_template('index.html'). But this time, there's a difference: you can write any name you want, but you need to give one parameter. The name doesn't matter; I gave the parameter name "sayı".
You can define this in the upper lines or directly here:
Python:
return render_template("index.html", sayı=15)On the HTML side, you need to specify this variable name inside {{ parameter_name }}.
Examples
Control if a number exists and display it in HTML:
Python:
from flask import Flask, render_template
app = Flask([B]name[/B])
@app.route("/")def main():return render_template("index.html", sayı=5)
if [B]name[/B] == "[B]main[/B]":app.run(debug=True)HTML:
HTML:
<!DOCTYPE html>
<html lang="en"><head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Arge Flask App</title></head><body> {% if sayı %} <p>{{ sayı }}</p> {% endif %}</body></html>Using ELSE
Python:
Python:
from flask import Flask, render_template
app = Flask([B]name[/B])
@app.route("/")def main():return render_template("index.html", deneme="Naber")
app.run(debug=True)HTML:
HTML:
<!DOCTYPE html>
<html lang="en"><head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Arge Flask App</title></head><body> {% if sayı %} <h1>{{ sayı }}</h1> {% else %} <p>Bişey Olmadı</p> {% endif %}</body></html>Using ENDIF
Python:
Python:
from flask import Flask, render_template
app = Flask([B]name[/B])
@app.route("/")def main():return render_template("index.html", sayı=5)
app.run(debug=True)HTML:
HTML:
<!DOCTYPE html>
<html lang="en"><head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Arge Flask App</title></head><body> {% if sayı %} <p>{{ sayı }}</p> {% endif %} <p>İşlem Başarı İle Tamamlandı</p></body></html>Sending More Than Just Numbers
Of course, we can send more than just numbers. For example, let's make a request to THT and display the status code.
Python:
Python:
Python:
from flask import Flask, render_templateimport requests
app = Flask([B]name[/B])
r = requests.get(url="[URL]https://turkhackteam.org/[/URL]")
@app.route("/")def main():return render_template("index.html", status=r.status_code)
app.run(debug=True)HTML:
HTML:
<!DOCTYPE html>
<html lang="en"><head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Arge Flask App</title></head><body> {% if status %} <h1>{{ status }}</h1> {% endif %}</body></html>Example For Loop
Python:
Python:
from flask import Flask, render_template
app = Flask([B]name[/B])
numaralar = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
@app.route("/")def main():return render_template('index.html', sayılar=numaralar)
if [B]name[/B] == "[B]main[/B]":app.run(debug=True)HTML:
HTML:
<!DOCTYPE html>
<html lang="en"><head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Arge Flask App</title></head><body> {% for donguler in sayılar %} <p>{{ donguler }}</p> {% endfor %}</body></html>That's it for now. In the coming days, I will update the topic by adding database operations, sending data, API creation, and more.
