Kuidas kolbi abil veebirakendust koostada ja pilve juurutada

Sissejuhatus

Igas jaotises näitan koodijuppe, mida saate jälgida. Kõik õpetuses kasutatud kood on saadaval selles GitHubi hoidlas.

Mis on HTTP ja mida see on seotud kolbiga?

HTTP on veebisaitide protokoll. Internet kasutab seda arvutite ja serveritega suhtlemiseks ja suhtlemiseks. Lubage mul tuua teile näide selle kohta, kuidas te seda igapäevaselt kasutate.

Kui sisestate oma brauseri aadressiribale veebisaidi nime ja vajutate sisestusklahvi. Juhtub see, et HTTP-päring on serverile saadetud.

Näiteks kui lähen oma aadressiribale ja tippin google.com ja vajutan siis sisestusklahvi, saadetakse Google'i serverile HTTP-päring. Google Server saab päringu kätte ja peab välja mõtlema, kuidas seda taotlust tõlgendada. Google Server saadab tagasi HTTP-vastuse, mis sisaldab teavet, mille minu veebibrauser saab. Seejärel kuvatakse see, mida te brauseris lehel küsisite.

Kuidas kolb on seotud?

Kirjutame koodi, mis hoolitseb serveripoolse töötlemise eest. Meie kood võtab vastu päringuid. See selgitab välja, mida need taotlused käsitlevad ja mida nad küsivad. Samuti selgitatakse välja, milline vastus kasutajale saata.

Selle kõige tegemiseks kasutame kolbi.

Mis on kolb?

See muudab veebirakenduse kujundamise protsessi lihtsamaks. Kolb laseb meil keskendudaselle kohta, mida kasutajad taotlevad ja millist vastust anda.

Lisateave mikroraamistike kohta.

Kuidas kolbirakendus töötab?

Kood võimaldab meil käitada veebi põhirakendust, mida saaksime teenida, nagu see oleks veebisait.

from flask import Flask app = Flask(__name__) @app.route("/") def home(): return "Hello, World!" if __name__ == "__main__": app.run(debug=True)

See koodilõik on salvestatud meie main.py.

Rida 1: siin impordime mooduli Flask ja loome moodulist Flask Flaski veebiserveri.

3. rida: __name__ tähendab seda praegust faili . Sel juhul on see main.py. Praegune fail esindab minu veebirakendust.

Loome klassi Flask eksemplari ja nimetame seda rakenduseks. Siin loome uue veebirakenduse.

5. rida: see tähistab vaikelehte. Näiteks kui lähen kaldkriipsu järel veebisaidile nagu „google.com/”, kus pole midagi. Siis on see Google'i vaikeleht.

Rida 6–7 : Kui kasutaja läheb minu veebisaidile ja ta läheb vaikelehele (pärast kaldkriipsu pole midagi), siis aktiveeritakse allpool olev funktsioon.

9. rida: Pythoni skripti käivitamisel määrab Python selle käivitamisel skriptile nime „__main__”.

Kui impordime teise skripti, takistab if-lause teiste skriptide käitamist. Kui käivitame main.py, muudab see nime __main__ ja alles siis aktiveeritakse see, kui lause.

10. rida: see käivitab rakenduse. Võttes debug=Truelubab võimalik Python vead ilmuvad veebilehel. See aitab meil vigu jälgida.

Proovime käivitada main.py

Minge oma terminalis või käsuviibas kausta, mis sisaldab teie main.py.Seejärel tehke py main.pyvõi python main.py. Terminalis või käsuviibal peaksite seda väljundit nägema.

Oluline osa on seal, kus öeldakse Running on //127.0.0.1:5000/.

127.0.0.1 tähendab seda kohalikku arvutit. Kui te ei tea selle tähendust (nagu ma ei teadnud, kui alustasin - see artikkel on tõesti kasulik), on peamine idee, et 127.0.0.1 ja localhost viitavad sellele kohalikule arvutile.

Minge sellele aadressile ja peaksite nägema järgmist:

Kolbiga lõbusam

Varem nägite, mis juhtus, kui jooksime main.py ühe marsruudiga, mis oli app.route (“/”).

Lisame veel marsruute, et näeksite erinevust.

from flask import Flask app = Flask(__name__) @app.route("/") def home(): return "Hello, World!" @app.route("/salvador") def salvador(): return "Hello, Salvador" if __name__ == "__main__": app.run(debug=True)

In read 9-11 . lisasime uue marsruudi, seekord / salvadorile.

Nüüd käivitage uuesti main.py ja minge saidile// kohalik host: 5000 / salvador.

Siiani oleme teksti tagasi saatnud. Muudame oma veebisaidi HTML-i ja CSS-i lisamisega kenamaks.

HTML, CSS ja virtuaalsed keskkonnad

HTML ja mallid kolvis

Kõigepealt looge uus HTML-fail. Helistasin oma kodule.html.

Siin on mõned koodid alustamiseks.

    Flask Tutorial   

My First Try Using Flask

Flask is Fun

Oluline punkt, mida meeles pidada

Flask Framework otsib HTML-faile kaustast, mida nimetatakse mallideks. Peate looma mallide kausta ja panema kõik oma HTML-failid sinna.

Nüüd peame muutma oma main.py, et saaksime oma loodud HTML-faili vaadata.

from flask import Flask, render_template app = Flask(__name__) @app.route("/") def home(): return render_template("home.html") @app.route("/salvador") def salvador(): return "Hello, Salvador" if __name__ == "__main__": app.run(debug=True) We made two new changes

Line 1: We imported render_template() method from the flask framework. render_template() looks for a template (HTML file) in the templates folder. Then it will render the template for which you ask. Learn more about render_templates() function.

Line 7: We change the return so that now it returns render_template(“home.html”). This will let us view our HTML file.

Now visit your localhost and see the changes: //localhost:5000/.

Let’s add more pages

Let’s create an about.html inside the templates folder.

    About Flask   

About Flask

Flask is a micro web framework written in Python.

Applications that use the Flask framework include Pinterest, LinkedIn, and the community web page for Flask itself.

Let’s make a change similar to what we did before to our main.py.

from flask import Flask, render_template app = Flask(__name__) @app.route("/") def home(): return render_template("home.html") @app.route("/about) def about(): return render_template("about.html") if __name__ == "__main__": app.run(debug=True)

We made three new changes:

Line 9: Change the route to"/about".

Line 10: Change the function so it is nowdef about():

Line 11: Change the return so that now it returns render_template("about.html").

Now see the changes: //localhost:5000/about.

Let’s Connect Both Pages with a Navigation

To connect both pages we can have a navigation menu on the top. We can use Flask to make the process of creating a navigation menu easier.

First, let’s create a template.html. This template.html will serve as a parent template. Our two child templates will inherit code from it.

     Flask Parent Template 

First Web App

  • Home
  • About
{% block content %} {% endblock %}

Line 13–14: We use the function calledurl_for(). It accepts the name of the function as an argument. Right now we gave it the name of the function. More information on url_for() function.

The two lines with the curly brackets will be replaced by the content of home.html and about.html. This willdepend on the URL in which the user is browsing.

These changes allow the child pages (home.html and about.html) to connect to the parent (template.html). This allows us to not have to copy the code for the navigation menu in the about.html and home.html.

Content of about.html:

    About Flask   {% extends "template.html" %} {% block content %} 

About Flask

Flask is a micro web framework written in Python.

Applications that use the Flask framework include Pinterest, LinkedIn, and the community web page for Flask itself.

{% endblock %}

Content of home.html:

    Flask Tutorial   {% extends "template.html" %} {% block content %} 

My First Try Using Flask

Flask is Fun

{% endblock %}

Let’s try adding some CSS.

Adding CSS to Our Website

An important note to remember

In the same way as we created a folder called templates to store all our HTML templates, we need a folder called static.

In static, we will store our CSS, JavaScript, images, and other necessary files. That is why it is important that you should create a CSSfolder to store your stylesheets. After you do this, your project folder should look like this:

Linking our CSS with our HTML file

Our template.html is the one that links all pages. We can insert the code here and it will be applicable to all child pages.

    Flask Parent Template 

First Web App

  • Home
  • About
{% block content %} {% endblock %}

Line 7: Here we are giving the path to where the template.css is located.

Now see the changes: //localhost:5000/about.

Moving Forward with Flask and virtualenv

Now that you are familiar with using Flask, you may start using it in your future projects. One thing to always do is use virtualenv.

Why use virtualenv?

You may use Python for others projects besides web-development.

Your projects might have different versions of Python installed, different dependencies and packages.

We use virtualenv to create an isolated environment for your Python project. This means that each project can have its own dependencies regardless of what dependencies every other project has.

Getting started with virtualenv

First, run this command on your command prompt or terminal:

pip install virtualenv

Second, do the following:

virtualenv “name of virtual environment”

Here you can give a name to the environment. I usually give it a name of virtual. It will look like this: virtualenv virtual.

After setting up virtual environment, check your project folder. It should look like this. The virtual environment needs to be created in the same directory where your app files are located.

Activating the virtual environment

Now go to your terminal or command prompt. Go to the directory that contains the file called activate. The file called activate is found inside a folder called Scripts for Windows and bin for OS X and Linux.

For OS X and Linux Environment:

$ name of virtual environmnet/bin/activate

For Windows Environment:

name of virtual environment\Scripts\activate

Since I am using a Windows machine, when I activate the environment it will look like this:

The next step is to install flask on your virtual environment so that we can run the application inside our environment. Run the command:

pip install flask

Run your application and go to //localhost:5000/

We finally made our web application. Now we want to show the whole world our project.

(More information on virtualenv can be found in the following guides on virtualenv and Flask Official Documentation)

Let’s send it to the Cloud

To show others the project we made, we will need to learn how to use Cloud Services.

Deploy Your Web Application to the Cloud

To deploy our web application to the cloud, we will use Google App Engine (Standard Environment). This is an example of a Platform as a Service (PaaS).

PaaS viitab operatsioonisüsteemide ja nendega seotud teenuste tarnimisele Internetis ilma allalaadimiste või installimiseta . Lähenemisviis võimaldab klientidel luua ja juurutada rakendusi, ilma et peaksid investeerima alusinfrastruktuuri (Lisateavet PaaSi kohta vaadake TechTargetist).

Google App Engine on platvorm kui teenusepakkumine, mis võimaldab arendajatel ja ettevõtetel ehitada ja käitada rakendusi Google'i täiustatud infrastruktuuri - TechOpedia abil.

Enne kui alustad:

Teil on vaja Google'i kontot . Kui olete konto loonud, minge Google Cloud Platform Console'i ​​ja looge uus projekt. Samuti peate installima Google Cloud SDK.

Selle õpetuse lõpus näeb teie projekti struktuur välja selline.

We will need to create three new files: app.yaml, appengine_config.py, and requirements.txt.

Content of app.yaml:

runtime: python27 api_version: 1 threadsafe: true handlers: - url: /static static_dir: static - url: /.* script: main.app libraries: - name: ssl version: latest

If you were to check Google’s Tutorial in the part where they talk about content of the app.yaml, it does not include the section where I wrote about libraries.

When I first attempted to deploy my simple web app, my deployment never worked. After many attempts, I learned that we needed to include the SSL library.

The SSL Library allows us to create secure connections between the client and server. Every time the user goes to our website they will need to connect to a server run by Google App Engine. We need to create a secure connection for this. (I recently learned this, so if you have a suggestions for this let me know!)

Content of appengine_config.py:

from google.appengine.ext import vendor # Add any libraries installed in the "lib" folder. vendor.add('lib')

Content of requirements.txt:

Flask Werkzeug

Now inside our virtual environment (make sure your virtualenv is activated),we are going to install the new dependencies we have in requirements.txt. Run this command:

pip install -t lib -r requirements.txt

-t lib: This flag copies the libraries into a lib folder, which uploads to App Engine during deployment.

-r requirements.txt: Tells pip to install everything from requirements.txt.

Deploying the Application

To deploy the application to Google App Engine, use this command.

gcloud app deploy

I usually include — project [ID of Project]

This specifies what project you are deploying. The command will look like this:

gcloud app deploy --project [ID of Project]

The Application

Now check the URL of your application. The application will be store in the following way:

"your project id".appspot.com

My application is here: //sal-flask-tutorial.appspot.com

Conclusion

From this tutorial, you all learned how to:

  • Use the framework called Flask to use Python as a Server Side Language.
  • Learned how to use HTML, CSS, and Flask to make a website.
  • Learned how to create Virtual Environments using virtualenv.
  • Use Google App Engine Standard Environment to deploy an application to the cloud.

What I learned

I learned three important things from this small project.

First, I learned about the difference between a static website and a web application

Static Websites:

  • Means that the server is serving HTML, CSS, and JavaScript files to the client. The content of the site does not change when the user interacts with it.

Web Applications:

  • A web application or dynamic website generates content based on retrieved data (most of the time is a database) that changes based on a user’s interaction with the site. In a web application, the server is responsible for querying, retrieving, and updating data. This causes web applications to be slower and more difficult to deploy than static websites for simple applications (Reddit).

Server Side and Client Side:

  • I learned that a web application has two sides. The client side and the server side. The client side is what the user interacts with and the server side is where the all the information that the user inputted is processed.

Second, I learned about Cloud Services

Most of my previous projects were static websites, and to deploy them I used GitHub Pages. GitHub Pages is a free static site hosting service designed to host projects from a GitHub Repository.

When working with web applications, I could not use GitHub Pages to host them. GitHub Pages is only meant for static websites not for something dynamic like a web application that requires a server and a database. I had to use Cloud Services such as Amazon Web Services or Heroku

Third, I learned how to use Python as a Server Side Language

To create the server side of the web application we had to use a server side language. I learned that I could use the framework called Flask to use Python as the Server Side Language.

Next Steps:

You can build all sorts of things with Flask. I realized that Flask helps make the code behind the website easier to read. I have made the following applications during this summer of 2018 and I hope to make more.

Personal Projects

  • A Twilio SMS App
  • My Personal Website

During my internship

  • Part of a project where I learned about Docker and Containers

Here is the list of resources that helped me create this tutorial:

  • “App Engine — Build Scalable Web & Mobile Backends in Any Language | App Engine | Google Cloud.” Google, Google, cloud.google.com/appengine/.
  • “Building a Website with Python Flask.” PythonHow, pythonhow.com/building-a-website-with-python-flask/.
  • “Flask — Lecture 2 — CS50’s Web Programming with Python and JavaScript.” YouTube, 6 Feb. 2018, youtu.be/j5wysXqaIV8.
  • “Getting Started with Flask on App Engine Standard Environment | App Engine Standard Environment for Python | Google Cloud.” Google, Google, cloud.google.com/appengine/docs/standard/python/getting-started/python-standard-env.
  • “Installation.” Welcome | Flask (A Python Microframework), flask.pocoo.org/docs/0.12/installation/.
  • “Python — Deploying Static Flask Sites for Free on Github Pages.” Reddit, www.reddit.com/r/Python/comments/1iewqt/deploying_static_flask_sites_for_free_on_github/.
  • Päris Python. "Pythoni virtuaalsed keskkonnad: aabits - tõeline Python." Real Python , Real Python, 7. august 2018, realpython.com/python-virtual-environments-a-primer/.
  • „Mis on pilveteenused? - määratlus saidilt WhatIs.com. " SearchITChannel , searchitchannel.techtarget.com/definition/cloud-services.
  • „Mis on Google App Engine (GAE)? - Definitsioon Techopediast. " Techopedia.com , www.techopedia.com/definition/31267/google-app-engine-gae.

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