You should be able to find articles and tutorials on all these topics on LinuxHint.com<\/a><\/p>\n I will be using Python 3 on Debian 9 Stretch in this article. If you\u2019re using Python 2, you will have to adjust a little bit. You should be able to figure it out yourself as it will be simple as writing python instead of python3 and pip instead of pip3.<\/p>\n To put it simply, virtual environment is used to isolate one Python app from another. The Python package used to do that is virtualenv.<\/p>\n You can easily install virtualenv using PIP on your computer with the following command:<\/p>\n $ sudo -H pip3 install virtualenv<\/p>\n Now create a project directory (let\u2019s call it pyrest\/) with the following command:<\/p>\n Now create a Python virtual environment on the pyrest\/ project directory with the following command:<\/p>\n Now navigate into the project directory with the following command:<\/p>\n Then, activate the Python virtual environment with the following command:<\/p>\n Finally, run the following command to install the Flask Python library:<\/p>\n In this section, I will write a hello world program in Python Flask.<\/p>\n First, create a file hello.py in your project directory:<\/p>\n Now add the following lines to hello.py file and save it.<\/p>\n In the next section, I will show you how to run Flask scripts.<\/p>\n Now to start the hello.py Flask server, run the following command:<\/p>\n As you can see, the server has started on http:\/\/127.0.0.1:8080.<\/p>\n Now, you can access the Flask server http:\/\/127.0.0.1:8080 from the web browser or API testing softwares such as Postman. I am going to use CURL.<\/p>\n $ curl http:\/\/127.0.0.1:8080<\/p>\n As you can see, the correct output is printed on the screen.<\/p>\n Congrats! Flask is working.<\/p>\n GET request on REST API is used to fetch information from the API server. You set some API endpoints and do a GET request on that end point. It\u2019s simple.<\/p>\n First, create a new file get.py in your project directory with the following command:<\/p>\n Now add the following lines in your get.py file and save it.<\/p>\n Here, on line 1, the Flask constructor function and jsonify function is imported from the flask module.<\/p>\n On line 3, a Flask object is created and stored on app variable.<\/p>\n On line 5, I created a Python array of dictionaries of some dummy data and stored it in the accounts variable.<\/p>\n On line 10, I defined the API endpoint \/accounts and the request method, which is GET.<\/p>\n On line 11, I defined the function getAccounts(). getAccounts() function will execute when a GET request to \/accounts endpoint is made.<\/p>\n Line 12, which is a part of getAccounts() function, I converted the accounts array of dictionaries to JSON using jsonify() function and returned it.<\/p>\n On line 14-15, I called the app.run() to tell Flask to run the API server on port 8080.<\/p>\n Now run the Flask API server with the following command:<\/p>\n The server has started on port 8080.<\/p>\n Now make a GET request to the \/accounts endpoint with CURL as follows:<\/p>\n $ curl http:\/\/127.0.0.1:8080\/accounts<\/p>\n As you can see, the accounts data is displayed as JSON format on GET request on \/accounts endpoint.<\/p>\n You can also get specific account data as well. To do that, I am going to create another API endpoint \/account\/<id>. Here, <id> will be the ID the account holder. The ID here is the index of the array.<\/p>\n Edit the get.py script and add the marked lines to it.<\/p>\n Here, on line 14, I defined the API endpoint \/account\/<id> and the method to be used, which is GET.<\/p>\n On line 15-17, the function getAccount() for the API endpoint \/account\/<id> is defined. The getAccount() function accepts a id as an argument. The value of <id> from the API endpoint is set to the id variable of getAccount() function.<\/p>\n On line 16, the id variable is converted to an integer. I also deduced 1 from the id variable. Because the array index starts from 0. I want to start the account ID from 1. So if I put 1 as the account <id>, 1 \u2013 1 = 0, I will get the element at index 0 from the array accounts.<\/p>\n On line 17, the array at index <id> is returned as JSON.<\/p>\n The rest of the codes are the same.<\/p>\n Now run the API server again.<\/p>\n I requested data for account 1 and 2 separately and I got the expected output as you can see from the screenshot below.<\/p>\n $ curl http:\/\/127.0.0.1:8080\/account\/1 Now I am going to rename get.py to api.py and add an API endpoint \/account for adding new data.<\/p>\n Rename get.py to api.py:<\/p>\n First, add the lines (19-26) as marked in the screenshot below to the api.py file.<\/p>\n Now run the api.py server:<\/p>\n To insert new data into the \/account endpoint, run the following command:<\/p>\n $ curl -X POST -H “Content-Type: application\/json” -d ‘{“name”: “Shovon”, “balance”: 100}’ NOTE:<\/u> Here, \u2018{\u201cname\u201d: \u201cShovon\u201d, \u201cbalance\u201d: 100}\u2019 is the JSON input data.<\/p>\n The data should be inserted.<\/p>\n As you can see, the new data is added.<\/p>\n So that\u2019s it for this article. Thanks for reading this article.<\/p>\nSetting Up Virtual Environment:<\/h2>\n
Writing Your First Flask Script:<\/h3>\n
![\"\"](\"https:\/\/linuxhint.com\/wp-content\/uploads\/2018\/10\/1-6.png\")
<\/p>\nRunning Flask Script:<\/h3>\n
![\"\"](\"https:\/\/linuxhint.com\/wp-content\/uploads\/2018\/10\/2-6.png\")
<\/p>\n![\"\"](\"https:\/\/linuxhint.com\/wp-content\/uploads\/2018\/10\/3-6.png\")
<\/p>\nAccessing Data Using GET in REST API:<\/h3>\n
![\"\"](\"https:\/\/linuxhint.com\/wp-content\/uploads\/2018\/10\/4-5.png\")
<\/p>\n![\"\"](\"https:\/\/linuxhint.com\/wp-content\/uploads\/2018\/10\/5-5.png\")
<\/p>\n![\"\"](\"https:\/\/linuxhint.com\/wp-content\/uploads\/2018\/10\/6-4.png\")
<\/p>\n![\"\"](\"https:\/\/linuxhint.com\/wp-content\/uploads\/2018\/10\/7-4.png\")
<\/p>\n![\"\"](\"https:\/\/linuxhint.com\/wp-content\/uploads\/2018\/10\/8-3.png\")
<\/p>\n
\n$ curl http:\/\/127.0.0.1:8080\/account\/2<\/p>\n![\"\"](\"https:\/\/linuxhint.com\/wp-content\/uploads\/2018\/10\/9-2.png\")
<\/p>\nAdding Data Using POST in REST API:<\/h3>\n
![\"\"](\"https:\/\/linuxhint.com\/wp-content\/uploads\/2018\/10\/10-3.png\")
<\/p>\n![\"\"](\"https:\/\/linuxhint.com\/wp-content\/uploads\/2018\/10\/11-2.png\")
<\/p>\n
\nhttp:\/\/127.0.0.1:8080\/account<\/p>\n![\"\"](\"https:\/\/linuxhint.com\/wp-content\/uploads\/2018\/10\/12-2.png\")
<\/p>\n![\"\"](\"https:\/\/linuxhint.com\/wp-content\/uploads\/2018\/10\/13-2.png\")
<\/p>\n