What is Web API?
A Web API (Application Programming Interface) enables communication between different applications over the web.
Uses standardized protocols like HTTP, data formats like JSON/XML.
Allows automation and data exchange across platforms.
What is Web API Used For?
Data Exchange: Fetching or sending structured information.
Third-Party Integration: Payment gateways, social media APIs, etc.
Microservices Architecture: Independent services working together.
Where is Web API Used?
Web Applications: Frontend communicates with backend via API.
Mobile Apps: Sends API requests to retrieve data.
IoT Devices: Smart devices sync via API calls.
Cloud Services: SaaS applications expose APIs for automation.
What is Flask?
Flask is a web application framework written in Python.
It is developed by Armin Ronacher, who leads an international group of Python enthusiasts named Pocco.
Prerequisite
It is recommended that Flask should be installed on Python 2.7.
How to Install Flask
pip install flask
E:\Software\Google Drive\PRWATECH\BATCH-A>C:\Users\user\AppData\Local\Programs\Python\Python38-32\Scripts\pip install flask
Collecting flask
Downloading Flask-1.1.2-py2.py3-none-any.whl (94 kB)
|████████████████████████████████| 94 kB 325 kB/s
Requirement already satisfied: Werkzeug>=0.15 in c:\users\user\appdata\local\programs\python\python38-32\lib\site-packages (from flask) (1.0.1)
Requirement already satisfied: Jinja2>=2.10.1 in c:\users\user\appdata\local\programs\python\python38-32\lib\site-packages (from flask) (2.11.1)
Requirement already satisfied: itsdangerous>=0.24 in c:\users\user\appdata\local\programs\python\python38-32\lib\site-packages (from flask) (1.1.0)
Requirement already satisfied: click>=5.1 in c:\users\user\appdata\local\programs\python\python38-32\lib\site-packages (from flask) (7.1.1)
Requirement already satisfied: MarkupSafe>=0.23 in c:\users\user\appdata\local\programs\python\python38-32\lib\site-packages (from Jinja2>=2.10.1->flask) (1.1.1)
Installing collected packages: flask
Successfully installed flask-1.1.2
After installing flask, now its time to code and understand the fundamentals.
Below code is the very basic code to host an web api.
from flask import Flask #Importing Flask Module
app=Flask("mywebsite") #Creating Flask object.
#Business logic layer, producing result via api
@app.route('/') #The route() function of the Flask class is a decorator, which tells the application which URL should call the associated function.
def defaultmethod(): #Creating api, which is a default method when we run the website.
return 'This is default method'
app.run() #Running the web application .
When the application is run, the application is hosted on local machine and exposed via url as shown below.
E:\Software\Google Drive\PRWATECH\BATCH-A> cd "e:\Software\Google Drive\PRWATECH\BATCH-A" && cmd /C "C:\Users\user\AppData\Local\Programs\Python\Python38-32\python.exe c:\Users\user\.vscode\extensions\ms-python.python-2020.5.80290\pythonFiles\lib\python\debugpy\no_wheels\debugpy\launcher 51318 -- "e:\Software\Google Drive\PRWATECH\BATCH-A\learningflask.py" "
* Serving Flask app "mywebsite" (lazy loading)
* Environment: production
WARNING: This is a development server. Do not use it in a production deployment.
Use a production WSGI server instead.
* Debug mode: off
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
Focus on the last line, it says "Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)"
Now go to the browser, preferably chrome, and open the web application by url.
The result is presented in the form of string published on the html page.
Take away with the above example.
app.route('/') is a decorator, which the which tells the application which URL should call the associated function.
‘/’ URL is bound with default() function. Hence, when the home page of web server is opened in browser, the output of this function will be rendered.
Debug mode
A Flask application is started by calling the run() method. However, while the application is under development, it should be restarted manually for each change in the code. To avoid this inconvenience, enable debug support. The server will then reload itself if the code changes. It will also provide a useful debugger to track the errors if any, in the application.
Routing Continues
Now if we want to navigate api using name,
from flask import Flask #Importing Flask Module
app=Flask("mywebsite") #Creating Flask object.
#Business logic layer, producing result via api
@app.route('/') #The route() function of the Flask class is a decorator, which tells the application which URL should call the associated function.
def defaultmethod(): #Creating api, which is a default method when we run the website.
return 'This is default function'
@app.route('/m1') #This help to call the named api
def m1():
return 'This is M1 Method'
app.run(debug=True) #Running the webapplication .
How to call the named api,
http://127.0.0.1:5000/m1
Multilevel Api Calling
@app.route('/m1/m2')#This is multi level api calling.
def m2():
return 'This is M2 Method'
Passing parameter to the api.
@app.route('/m3/<param>')#Passing parameter to the API
def m3(param):
return 'This is M3 Method :: '+param
Rules can be set to pass specific datatype parameters.
@app.route('/m4/<int:param>')#passing parameters to the api
def m4(param):
returndata='Type of parameter passed::'+str(param)
return 'This is M4 Method :: '+returndata
Test case
Consuming WebAPI
#write a code to consume the API and print the response using flask
import requests
from flask import Flask, jsonify
def consume_api():
# URL of the API endpoint
url = 'http://127.0.0.1:5000/myfunction'
# Make a GET request to the API
response = requests.get(url)
# Check if the request was successful (status code 200)
if response.status_code == 200:
# Parse the JSON response
data = response.json()
print(data)
else:
print(f"Error: {response.status_code}")
consume_api()
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