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Flask: Develop Web Applications in Python

Solution: Updating and Deleting Pets

Explore how to implement secure update and delete functionality for pet records in a Flask application. Learn to create dedicated edit pages, handle form validation, protect database integrity with transactions and rollbacks, and manage routes for efficient record operations.

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To manage database records securely while preserving our existing frontend style structure, we must replicate our proven form design patterns across our new administrative modules. This solution introduces an independent edit page template and dedicated controller hooks that maintain uniform line-breaking conventions and style containers throughout the platform.

The complete code layout below demonstrates the fully integrated implementation for our form data definitions file.

Python 3.14.0
from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, SubmitField, IntegerField
from wtforms.validators import InputRequired, Email, EqualTo
class LoginForm(FlaskForm):
    email = StringField('Email', validators=[InputRequired(), Email()])
    password = PasswordField('Password', validators=[InputRequired()])
    submit = SubmitField('Login')
    
class SignUpForm(FlaskForm):
    email = StringField('Email', validators=[InputRequired(), Email()])
    password = PasswordField('Password', validators=[InputRequired()])
    confirm_password = PasswordField('Confirm Password', validators=[InputRequired(), EqualTo('password')])
    submit = SubmitField('Sign Up')
class EditPetForm(FlaskForm):
    name = StringField("Pet's Name", validators=[InputRequired()])
    age = IntegerField("Pet's Age", validators=[InputRequired()])
    bio = StringField("Pet's Bio", validators=[InputRequired()])
    submit = SubmitField("Update Pet")

  • Lines 16–20: We declare our form mapping configuration container EditPetForm. We utilize an explicit IntegerField for the animal’s age property to ensure strict parameter type compatibility with our relational database columns.

With our form data definitions updated, we refine our read-only dashboard overview presentation layer.

HTML
{% extends "base.html" %}
{% block title %}
    {% if cat %}
        {{ cat.name }} - Profile Details
    {% else %}
        404 - Profile Not Found
    {% endif %}
{% endblock %}
{% block content %}
    {% if cat %}
        <div>
            <h1>Meet {{ cat.name }}</h1>
            <div>
                <img src="{{ url_for('static', filename=cat.image) }}" alt="{{ cat.name }}" width="300">
                <div>
                    <h3>Age: {{ cat.age }} years old</h3>
                    <p><strong>Biography:</strong> {{ cat.bio }}</p>
                    <p><a href="{{ url_for('homepage') }}">← Return to Dashboard</a></p>
                    <p><a href="{{ url_for('edit_pet', cat_id=cat.id) }}">✏️ Edit Pet Information</a></p>
                    <p><a href="{{ url_for('delete_pet', cat_id=cat.id) }}" onclick="return confirm('Are you sure you want to permanently delete this pet profile?');" style="color: red;">❌ Delete Pet Profile</a></p>
                </div>
            </div>
        </div>
    {% else %}
        <div>
            <h1>404 - Profile Not Found</h1>
            <p>No cat profile was found matching that specific identifier.</p>
            <p><a href="{{ url_for('homepage') }}">← Return to Dashboard</a></p>
        </div>
    {% endif %}
{% endblock %}
    ...