# Flask ```python 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 ``. Your function then receives the `` as a keyword argument. Optionally, you can use a converter to specify the type of the argument like ``. 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 ```python @app.route("/user/") # 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("/")` to accept the passed arguments. ```py 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 %}` to end a block of code. In `page.html`; ```py {% for item in content %}

{% endfor %} ``` In `file.py`: ```py @app.route("/page/) def func(): return render_template("page.html", content=["A", "B", "C"]) ``` ### Hyperlinks In `file.py`: ```py @app.route('/linked_page/') def cool_form(): return render_template('linked_page.html') ``` In `page.html`: ```html link text ``` ### CSS Put `style.css` inside `/static/style`. In `page.html`: ```html ``` ## Template Inheritance In `parent_template.html`: ```html {% block block_name %} {% endblock %} ``` The content of the block will be filled by the child class. In `child_template.html`: ```html {% extends "parent_template.html" %} {% block block_name} {{ super() }} {% endblock %} ```