Gain insights into developing web applications using Flask, a lightweight and easy-to-learn Python framework. Delve into techniques that make you a sought-after full-stack developer.

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This project-based course is a detailed guide to web application development using the increasingly popular Flask framework.

Flask is known for being simple, lightweight and having a small learning curve. If you've got some experience in Python, picking up Flask will be a breeze. It's got a booming job market and will put you on track to becoming an in-demand full-stack developer. What's not to love?

Flask: Develop Web Applications in Python

"""Flask Application for Paws Rescue Center."""
from flask import Flask, render_template, abort
from forms import SignUpForm

app = Flask(__name__)
app.config['SECRET_KEY'] = 'dfewfew123213rwdsgert34tgfd1234trgf'

"""Information regarding the Pets in the System."""
pets = [
            {"id": 1, "name": "Nelly", "age": "5 weeks", "bio": "I am a tiny kitten rescued by the good people at Paws Rescue Center. I love squeaky toys and cuddles."},
            {"id": 2, "name": "Yuki", "age": "8 months", "bio": "I am a handsome gentle-cat. I like to dress up in bow ties."},
            {"id": 3, "name": "Basker", "age": "1 year", "bio": "I love barking. But, I love my friends more."},
            {"id": 4, "name": "Mr. Furrkins", "age": "5 years", "bio": "Probably napping."}, 
        ]

"""Information regarding the Users in the System."""
users = [
            {"id": 1, "full_name": "Pet Rescue Team", "email": "team@pawsrescue.co", "password": "adminpass"},
        ]


@app.route("/")
def homepage():
    """View function for Home Page."""
    return render_template("home.html", pets = pets)


@app.route("/about")
def about():
    """View function for About Page."""
    return render_template("about.html")


@app.route("/details/<int:pet_id>")
def pet_details(pet_id):
    """View function for Showing Details of Each Pet.""" 
    pet = next((pet for pet in pets if pet["id"] == pet_id), None) 
    if pet is None: 
        abort(404, description="No Pet was Found with the given ID")
    return render_template("details.html", pet = pet)


@app.route("/signup", methods=["POST", "GET"])
def signup():
    """View function for Showing Details of Each Pet.""" 
    form = SignUpForm()
    if form.validate_on_submit():
        new_user = {"id": len(users)+1, "full_name": form.full_name.data, "email": form.email.data, "password": form.password.data}
        users.append(new_user)
        return render_template("signup.html", message = "Successfully signed up")
    return render_template("signup.html", form = form)

if __name__ == "__main__":
    app.run(debug=True, host="0.0.0.0", port=3000)


from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, SubmitField
from wtforms.validators import InputRequired, Email, EqualTo

class SignUpForm(FlaskForm):
    password = PasswordField('Password', validators = [InputRequired()])
    full_name = StringField('Full Name')
    email = StringField('Email',
                        validators = [InputRequired(), Email()])
    password = PasswordField('Password', validators = [InputRequired()])
    confirm_password = PasswordField('Confirm Password',
                                     validators = [InputRequired(), EqualTo('password')])
    submit = SubmitField('Sign Up')


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# Explanation
Let's breakdown the solution of this challenge to figure out how we solved it. 
## Modifications in `app.py`
We have used the `validate_on_submit()` function of the `FlaskForm` class at **line 47** in the `signup` view. This shortcut function only returns `true` when the data is both **submitted** and **valid**. Therefore, inside the `if` condition, we create a `new_user` dictionary with the data received from the `form`. Then, we `append()` this `new_user` to the `users` list. Afterward, we render the `signup.html` template again, this time without the `form`, but with a `message` variable to indicate success. 

Finally, in the case where `validate_on_submit()` returns `false`, we have returned the `signup.html` template, again, with the `form` object. 

## Modifications in `signup.html`
In the `signup.html` template, we made two major changes:
1. **Display errors:** we used a `for` loop in Jinja to print all the errors associated with a field underneath it. To give it the feel of an alert, we used the color `tomato` for its text. 
2. **Display success message:** as mentioned above, if the `new_user` is added to the `users` list, we send a variable called `message` to indicate success. In **line 13**, we check if this variable was received. Then, we print its value in **line 14** and close the `if` condition.

In this lesson, we will take a look at the solution to the challenge presented in the previous lesson.

Before Getting Started

Introduction to Flask

First Flask Application

Build File/Directory Explorer in Flask

Static Templates

Static Files

Dynamic Templates

Form Handling

Database

Operations on Models

Conclusion

Test a MEAN Stack Todo Application with JEST

Build an E-Learning Website Using Flask

Solution: Sign-Up Form Data Handling

Solution