Flask

from flask import Flask, render_template

app = Flask(__name__, template_folder="path_to_folder")    # create app

# template folder contains html pages
@app.route("/")    # define URLs
def index():

    return render_template("index.html")    # parse HTML page and return it


if __name__ == "__main__":
    # run server if server is single file
    app.run(debug=True, host="0.0.0.0")

@app.route("/page/") enables to access the page with url/page and url/page/. The same is possible using app.add_url_rule("/", "page", function).

Variable Rules

You can add variable sections to a URL by marking sections with <variable_name>.
Your function then receives the <variable_name> as a keyword argument.
Optionally, you can use a converter to specify the type of the argument like <converter:variable_name>.

Converter Type	Accepts
`string`	any text without a slash (default option)
`int`	positive integers
`float`	positive floating point values
`path`	strings with slashes
`uuid`	UUID strings

@app.route("/user/<string:username>")    # handle URL at runtime
def profile(username):
    return f"{escape(username)}'s profile'"

Redirection

url_for(endpoint, **values) is used to redirect passing keyworded arguments. It can be used in combination with @app.route("/<value>") to accept the passed arguments.

from flask import Flask, redirect, url_for

@app.route("/url")
def func():

    return redirect(url_for("html_file/function"))    # redirect to other page

Jinja Template Rendering (Parsing Python Code in HTML, CSS)

{% ... %} for Statements
{{ ... }} for Expressions to print to the template output
{# ... #} for Comments not included in the template output
# ... ## for Line Statements

Use {% block block_code %} to put a line python code inside HTML. Use {% end<block> %} to end a block of code.

In page.html;

<html>
    {% for item in content %}
        <p>{{item}}</p>
    {% endfor %}
</html>

In file.py:

@app.route("/page/)
def func():
    return render_template("page.html", content=["A", "B", "C"])

Hyperlinks

In file.py:

@app.route('/linked_page/')
def cool_form():
    return render_template('linked_page.html')

In page.html:

<!doctype html>
<html>
  <head>
  </head>

  <body>
    <a href="{{ url_for('linked_page') }}">link text</a>
  </body>
</html>

CSS

Put style.css inside /static/style.

In page.html:

<!doctype html>
<html>
  <head>
  </head>
    <link rel="stylesheet" href="{{ url_for('static', filename='style/style.css') }}">
  <body>

  </body>
</html>

Template Inheritance

In parent_template.html:

<html>
    <!-- html content -->
    {% block block_name %}
    {% endblock %}
    <!-- html content -->
</html>

The content of the block will be filled by the child class.

In child_template.html:

{% extends "parent_template.html" %}
{% block block_name}
    {{ super() }}  <!-- use parent's contents -->
    <!-- block content -->
{% endblock %}

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