Search icon CANCEL
Subscription
0
Cart icon
Your Cart (0 item)
Close icon
You have no products in your basket yet
Arrow left icon
Explore Products
Best Sellers
New Releases
Books
Videos
Audiobooks
Learning Hub
Free Learning
Arrow right icon
Building Web Applications with Flask
Building Web Applications with Flask

Building Web Applications with Flask: Use Python and Flask to build amazing web applications, just the way you want them!

Arrow left icon
Profile Icon Italo Maia Profile Icon Italo M Campelo Maia Profile Icon Gareth Dwyer Profile Icon Jack Stouffer
Arrow right icon
€29.99
Full star icon Full star icon Full star icon Full star icon Empty star icon 4 (1 Ratings)
Paperback Jun 2015 160 pages 1st Edition
eBook
€15.99 €23.99
Paperback
€29.99
Subscription
Free Trial
Renews at €18.99p/m
Arrow left icon
Profile Icon Italo Maia Profile Icon Italo M Campelo Maia Profile Icon Gareth Dwyer Profile Icon Jack Stouffer
Arrow right icon
€29.99
Full star icon Full star icon Full star icon Full star icon Empty star icon 4 (1 Ratings)
Paperback Jun 2015 160 pages 1st Edition
eBook
€15.99 €23.99
Paperback
€29.99
Subscription
Free Trial
Renews at €18.99p/m
eBook
€15.99 €23.99
Paperback
€29.99
Subscription
Free Trial
Renews at €18.99p/m

What do you get with Print?

Product feature icon Instant access to your digital eBook copy whilst your Print order is Shipped
Product feature icon Paperback book shipped to your preferred address
Product feature icon Download this book in EPUB and PDF formats
Product feature icon Access this title in our online reader with advanced features
Product feature icon DRM FREE - Read whenever, wherever and however you want
OR
Modal Close icon
Payment Processing...
tick Completed

Shipping Address

Billing Address

Shipping Methods
Table of content icon View table of contents Preview book icon Preview Book

Building Web Applications with Flask

Chapter 2. First App, How Hard Could it Be?

After a full chapter without a single line of code, you need this, right? In this chapter, we will write our first app explained line by line; we will also cover how to set up our environment, what tools to use for development, and how to work with HTML in our app.

Hello World

The first app one writes when learning a new technology is usually a Hello World app, which consists of the minimum possible code necessary to start a simple application and show the text "Hello World!". Let's do exactly that using Flask.

This book is optimized for Python 2.x, so, that's the version I advise you to use from now on. All the examples and code are aimed at that Python version, which is the default in most Linux distributions.

Prerequisites and tools

First, let's make sure our environment is properly configured. For this course, I assume you are using a Debian-like Linux distribution, such as Mint (http://www.linuxmint.com/) or Ubuntu (http://ubuntu.com/). All the instructions will be geared towards these systems.

Let's begin by installing the required Debian packages with apt-get as follows:

sudo apt-get install python-dev python-pip

This will install the Python development tools and libraries required for compiling Python packages, and pip: a neat tool you can use to install Python packages from the command line. On with it! Let's install our virtual environment managing tool:

sudo pip install virtualenvwrapper
echo "source /usr/local/bin/virtualenvwrapper.sh" >> ~/.bashrc

To explain what we just did: sudo tells our OS that we want administrative privileges to run the next command, and pip is the default Python package management tool and helps us install the virtualenvwrapper package...

Setting up a virtual environment

A virtual environment is the way Python isolates full package environments from one another. This means you can easily manage dependencies. Imagine you want to define the minimum necessary packages for a project; a virtual environment would be perfect to let you test and export the list of needed packages. We will discuss it later on. Now, create a new terminal pressing Ctrl + Shift + T on your keyboard and create our hello world environment like this:

mkvirtualenv hello
pip install flask

The first line creates our environment with the name "hello". You will also automatically load that environment into the current terminal. You can deactivate your virtual environment by typing deactivate and you can load it again with the following command:

workon hello  # substitute hello with the desired environment name if needed

The second line tells pip to install the Flask package in the current virtual environment, hello in this case.

Understanding the "Hello World" app

Given the environment set, what should we use to write our beautiful code? An editor or an IDE? If you're working on a low budget, try Light Table editor (http://lighttable.com/). Free, fast, and easy to use (Ctrl + Spacebar gives you access to all available options), it also has workspace support! Can't get any better for the money. If you're a lucky one with $200 to spare (or if you have a free license https://www.jetbrains.com/pycharm/buy/), just fork out for the PyCharm IDE which is pretty much the best IDE for Python Web development. Now let's move on.

Create a folder that will hold your project files (you don't need to but people will like you more if you do), as follows:

mkdir hello_world

Enter the new project folder and create the main.py file:

cd hello_world
touch main.py

The main.py file will have the whole "Hello World" application in it. Our main.py content should be like this:

# coding:utf-8
from flask...

Serving HTML pages

First, to make our hello function respond with HTML, all we have to do is change it like this:

def hello():
    return "<html><head><title>Hi there!</title></head><body>Hello World!</body></html>", 200

In the preceding example, hello is returning a HTML formatted string and a number. The string will be parsed as HTML by default while 200 is an optional HTTP code indicating a successful response. 200 is returned by default.

If you refresh your browser with F5, you'll notice that nothing has changed. That's why the Flask development server is not reloading when the source changes. That only happens when you run your application in debug mode. So let's do that:

app = Flask(__name__)
app.debug=True

Now go to the terminal where your application is running, type Ctrl + C then restart the server. You will notice a new output besides the URL where your server is running—something about "stat&quot...

Hello World


The first app one writes when learning a new technology is usually a Hello World app, which consists of the minimum possible code necessary to start a simple application and show the text "Hello World!". Let's do exactly that using Flask.

This book is optimized for Python 2.x, so, that's the version I advise you to use from now on. All the examples and code are aimed at that Python version, which is the default in most Linux distributions.

Left arrow icon Right arrow icon

Description

If you are a Python web developer who wants to learn more about developing applications in Flask and scaling them with industry-standard practices, this is the book for you.

Who is this book for?

If you are a Python web developer who wants to learn more about developing applications in Flask and scaling them with industry-standard practices, this is the book for you.

What you will learn

  • Create single page applications with Flask
  • Use macros, filters, tags, and control structures to render rich responses to user requests
  • Receive forms securely through formbased classes and WTForms
  • Utilize NoSQL or SQL databases to store user data seamlessly
  • Generate simple, yet powerful, REST services from your data models
  • Learn how to perform testdriven and behaviordriven developments in your Flask projects
  • Use Flask components to create maintainable nonflat projects
  • Harvest the power of extensions to build robust authorization and permission policies
Estimated delivery fee Deliver to Latvia

Premium delivery 7 - 10 business days

€25.95
(Includes tracking information)

Product Details

Country selected
Publication date, Length, Edition, Language, ISBN-13
Publication date : Jun 26, 2015
Length: 160 pages
Edition : 1st
Language : English
ISBN-13 : 9781784396152
Languages :
Tools :

What do you get with Print?

Product feature icon Instant access to your digital eBook copy whilst your Print order is Shipped
Product feature icon Paperback book shipped to your preferred address
Product feature icon Download this book in EPUB and PDF formats
Product feature icon Access this title in our online reader with advanced features
Product feature icon DRM FREE - Read whenever, wherever and however you want
OR
Modal Close icon
Payment Processing...
tick Completed

Shipping Address

Billing Address

Shipping Methods
Estimated delivery fee Deliver to Latvia

Premium delivery 7 - 10 business days

€25.95
(Includes tracking information)

Product Details

Publication date : Jun 26, 2015
Length: 160 pages
Edition : 1st
Language : English
ISBN-13 : 9781784396152
Languages :
Tools :

Packt Subscriptions

See our plans and pricing
Modal Close icon
€18.99 billed monthly
Feature tick icon Unlimited access to Packt's library of 7,000+ practical books and videos
Feature tick icon Constantly refreshed with 50+ new titles a month
Feature tick icon Exclusive Early access to books as they're written
Feature tick icon Solve problems while you work with advanced search and reference features
Feature tick icon Offline reading on the mobile app
Feature tick icon Simple pricing, no contract
€189.99 billed annually
Feature tick icon Unlimited access to Packt's library of 7,000+ practical books and videos
Feature tick icon Constantly refreshed with 50+ new titles a month
Feature tick icon Exclusive Early access to books as they're written
Feature tick icon Solve problems while you work with advanced search and reference features
Feature tick icon Offline reading on the mobile app
Feature tick icon Choose a DRM-free eBook or Video every month to keep
Feature tick icon PLUS own as many other DRM-free eBooks or Videos as you like for just €5 each
Feature tick icon Exclusive print discounts
€264.99 billed in 18 months
Feature tick icon Unlimited access to Packt's library of 7,000+ practical books and videos
Feature tick icon Constantly refreshed with 50+ new titles a month
Feature tick icon Exclusive Early access to books as they're written
Feature tick icon Solve problems while you work with advanced search and reference features
Feature tick icon Offline reading on the mobile app
Feature tick icon Choose a DRM-free eBook or Video every month to keep
Feature tick icon PLUS own as many other DRM-free eBooks or Videos as you like for just €5 each
Feature tick icon Exclusive print discounts

Frequently bought together


Stars icon
Total 103.97
Learning Flask Framework
€36.99
Mastering Flask
€36.99
Building Web Applications with Flask
€29.99
Total 103.97 Stars icon
Banner background image

Table of Contents

11 Chapters
1. Flask in a Flask, I Mean, Book Chevron down icon Chevron up icon
2. First App, How Hard Could it Be? Chevron down icon Chevron up icon
3. Man, Do I Like Templates! Chevron down icon Chevron up icon
4. Please Fill in This Form, Madam Chevron down icon Chevron up icon
5. Where Do You Store Your Stuff? Chevron down icon Chevron up icon
6. But I Wanna REST Mom, Now! Chevron down icon Chevron up icon
7. If Ain't Tested, It Ain't Game, Bro! Chevron down icon Chevron up icon
8. Tips and Tricks or Flask Wizardry 101 Chevron down icon Chevron up icon
9. Extensions, How I Love Thee Chevron down icon Chevron up icon
10. What Now? Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

Rating distribution
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
(1 Ratings)
5 star 0%
4 star 100%
3 star 0%
2 star 0%
1 star 0%
Po-An, Yang Oct 10, 2015
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
It can be batter with python 3.
Amazon Verified review Amazon
Get free access to Packt library with over 7500+ books and video courses for 7 days!
Start Free Trial

FAQs

What is the delivery time and cost of print book? Chevron down icon Chevron up icon

Shipping Details

USA:

'

Economy: Delivery to most addresses in the US within 10-15 business days

Premium: Trackable Delivery to most addresses in the US within 3-8 business days

UK:

Economy: Delivery to most addresses in the U.K. within 7-9 business days.
Shipments are not trackable

Premium: Trackable delivery to most addresses in the U.K. within 3-4 business days!
Add one extra business day for deliveries to Northern Ireland and Scottish Highlands and islands

EU:

Premium: Trackable delivery to most EU destinations within 4-9 business days.

Australia:

Economy: Can deliver to P. O. Boxes and private residences.
Trackable service with delivery to addresses in Australia only.
Delivery time ranges from 7-9 business days for VIC and 8-10 business days for Interstate metro
Delivery time is up to 15 business days for remote areas of WA, NT & QLD.

Premium: Delivery to addresses in Australia only
Trackable delivery to most P. O. Boxes and private residences in Australia within 4-5 days based on the distance to a destination following dispatch.

India:

Premium: Delivery to most Indian addresses within 5-6 business days

Rest of the World:

Premium: Countries in the American continent: Trackable delivery to most countries within 4-7 business days

Asia:

Premium: Delivery to most Asian addresses within 5-9 business days

Disclaimer:
All orders received before 5 PM U.K time would start printing from the next business day. So the estimated delivery times start from the next day as well. Orders received after 5 PM U.K time (in our internal systems) on a business day or anytime on the weekend will begin printing the second to next business day. For example, an order placed at 11 AM today will begin printing tomorrow, whereas an order placed at 9 PM tonight will begin printing the day after tomorrow.


Unfortunately, due to several restrictions, we are unable to ship to the following countries:

  1. Afghanistan
  2. American Samoa
  3. Belarus
  4. Brunei Darussalam
  5. Central African Republic
  6. The Democratic Republic of Congo
  7. Eritrea
  8. Guinea-bissau
  9. Iran
  10. Lebanon
  11. Libiya Arab Jamahriya
  12. Somalia
  13. Sudan
  14. Russian Federation
  15. Syrian Arab Republic
  16. Ukraine
  17. Venezuela
What is custom duty/charge? Chevron down icon Chevron up icon

Customs duty are charges levied on goods when they cross international borders. It is a tax that is imposed on imported goods. These duties are charged by special authorities and bodies created by local governments and are meant to protect local industries, economies, and businesses.

Do I have to pay customs charges for the print book order? Chevron down icon Chevron up icon

The orders shipped to the countries that are listed under EU27 will not bear custom charges. They are paid by Packt as part of the order.

List of EU27 countries: www.gov.uk/eu-eea:

A custom duty or localized taxes may be applicable on the shipment and would be charged by the recipient country outside of the EU27 which should be paid by the customer and these duties are not included in the shipping charges been charged on the order.

How do I know my custom duty charges? Chevron down icon Chevron up icon

The amount of duty payable varies greatly depending on the imported goods, the country of origin and several other factors like the total invoice amount or dimensions like weight, and other such criteria applicable in your country.

For example:

  • If you live in Mexico, and the declared value of your ordered items is over $ 50, for you to receive a package, you will have to pay additional import tax of 19% which will be $ 9.50 to the courier service.
  • Whereas if you live in Turkey, and the declared value of your ordered items is over € 22, for you to receive a package, you will have to pay additional import tax of 18% which will be € 3.96 to the courier service.
How can I cancel my order? Chevron down icon Chevron up icon

Cancellation Policy for Published Printed Books:

You can cancel any order within 1 hour of placing the order. Simply contact [email protected] with your order details or payment transaction id. If your order has already started the shipment process, we will do our best to stop it. However, if it is already on the way to you then when you receive it, you can contact us at [email protected] using the returns and refund process.

Please understand that Packt Publishing cannot provide refunds or cancel any order except for the cases described in our Return Policy (i.e. Packt Publishing agrees to replace your printed book because it arrives damaged or material defect in book), Packt Publishing will not accept returns.

What is your returns and refunds policy? Chevron down icon Chevron up icon

Return Policy:

We want you to be happy with your purchase from Packtpub.com. We will not hassle you with returning print books to us. If the print book you receive from us is incorrect, damaged, doesn't work or is unacceptably late, please contact Customer Relations Team on [email protected] with the order number and issue details as explained below:

  1. If you ordered (eBook, Video or Print Book) incorrectly or accidentally, please contact Customer Relations Team on [email protected] within one hour of placing the order and we will replace/refund you the item cost.
  2. Sadly, if your eBook or Video file is faulty or a fault occurs during the eBook or Video being made available to you, i.e. during download then you should contact Customer Relations Team within 14 days of purchase on [email protected] who will be able to resolve this issue for you.
  3. You will have a choice of replacement or refund of the problem items.(damaged, defective or incorrect)
  4. Once Customer Care Team confirms that you will be refunded, you should receive the refund within 10 to 12 working days.
  5. If you are only requesting a refund of one book from a multiple order, then we will refund you the appropriate single item.
  6. Where the items were shipped under a free shipping offer, there will be no shipping costs to refund.

On the off chance your printed book arrives damaged, with book material defect, contact our Customer Relation Team on [email protected] within 14 days of receipt of the book with appropriate evidence of damage and we will work with you to secure a replacement copy, if necessary. Please note that each printed book you order from us is individually made by Packt's professional book-printing partner which is on a print-on-demand basis.

What tax is charged? Chevron down icon Chevron up icon

Currently, no tax is charged on the purchase of any print book (subject to change based on the laws and regulations). A localized VAT fee is charged only to our European and UK customers on eBooks, Video and subscriptions that they buy. GST is charged to Indian customers for eBooks and video purchases.

What payment methods can I use? Chevron down icon Chevron up icon

You can pay with the following card types:

  1. Visa Debit
  2. Visa Credit
  3. MasterCard
  4. PayPal
What is the delivery time and cost of print books? Chevron down icon Chevron up icon

Shipping Details

USA:

'

Economy: Delivery to most addresses in the US within 10-15 business days

Premium: Trackable Delivery to most addresses in the US within 3-8 business days

UK:

Economy: Delivery to most addresses in the U.K. within 7-9 business days.
Shipments are not trackable

Premium: Trackable delivery to most addresses in the U.K. within 3-4 business days!
Add one extra business day for deliveries to Northern Ireland and Scottish Highlands and islands

EU:

Premium: Trackable delivery to most EU destinations within 4-9 business days.

Australia:

Economy: Can deliver to P. O. Boxes and private residences.
Trackable service with delivery to addresses in Australia only.
Delivery time ranges from 7-9 business days for VIC and 8-10 business days for Interstate metro
Delivery time is up to 15 business days for remote areas of WA, NT & QLD.

Premium: Delivery to addresses in Australia only
Trackable delivery to most P. O. Boxes and private residences in Australia within 4-5 days based on the distance to a destination following dispatch.

India:

Premium: Delivery to most Indian addresses within 5-6 business days

Rest of the World:

Premium: Countries in the American continent: Trackable delivery to most countries within 4-7 business days

Asia:

Premium: Delivery to most Asian addresses within 5-9 business days

Disclaimer:
All orders received before 5 PM U.K time would start printing from the next business day. So the estimated delivery times start from the next day as well. Orders received after 5 PM U.K time (in our internal systems) on a business day or anytime on the weekend will begin printing the second to next business day. For example, an order placed at 11 AM today will begin printing tomorrow, whereas an order placed at 9 PM tonight will begin printing the day after tomorrow.


Unfortunately, due to several restrictions, we are unable to ship to the following countries:

  1. Afghanistan
  2. American Samoa
  3. Belarus
  4. Brunei Darussalam
  5. Central African Republic
  6. The Democratic Republic of Congo
  7. Eritrea
  8. Guinea-bissau
  9. Iran
  10. Lebanon
  11. Libiya Arab Jamahriya
  12. Somalia
  13. Sudan
  14. Russian Federation
  15. Syrian Arab Republic
  16. Ukraine
  17. Venezuela