Flask Templates and Forms

Introduction

Render HTML templates and handle form data in Flask applications.

Templates

from flask import render_template

@app.route("/")
def index():
    return render_template("index.html", title="Home")

# In template (index.html)
# {{ title }}
# {% for item in items %}
#   <li>{{ item }}</li>
# {% endfor %}

Jinja2 Template Engine

<!-- Variables -->
{{ name }}
{{ user.age }}

<!-- Conditionals -->
{% if user.logged_in %}
  Welcome, {{ user.name }}!
{% else %}
  Please log in.
{% endif %}

<!-- Filters -->
{{ name|upper }}
{{ date|datetime }}

Form Handling

from flask import request, redirect, url_for

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

Practice Problems

1. Create template inheritance
2. Handle form submission
3. Use Jinja2 filters
4. Display flash messages
5. Implement CSRF protection