APIs and Requests

APIs (Application Programming Interfaces) allow applications to communicate with each other. In Python, the requests library is commonly used to interact with APIs for sending HTTP requests and receiving responses.

Installing the `requests` Library

The requests library is not included in Python’s standard library. Install it using pip:

pip install requests

Basic HTTP Methods

Sending a GET Request

import requests

response = requests.get("https://jsonplaceholder.typicode.com/posts/1")
print(response.status_code)  # Output: 200 (HTTP status code)
print(response.json())       # Output: JSON data from the API

Sending a POST Request

data = {"title": "New Post", "body": "This is the content.", "userId": 1}
response = requests.post("https://jsonplaceholder.typicode.com/posts", json=data)

print(response.status_code)  # Output: 201 (Created)
print(response.json())       # Output: Newly created resource

Other HTTP Methods

PUT: Update a resource.
DELETE: Remove a resource.

# PUT request
response = requests.put("https://jsonplaceholder.typicode.com/posts/1", json={"title": "Updated Title"})
print(response.json())

# DELETE request
response = requests.delete("https://jsonplaceholder.typicode.com/posts/1")
print(response.status_code)  # Output: 200 (Success)

Response Object

The response object returned by requests contains useful attributes:

response = requests.get("https://jsonplaceholder.typicode.com/posts/1")

print(response.text)         # Raw response content
print(response.json())       # Parsed JSON data
print(response.status_code)  # HTTP status code
print(response.headers)      # Response headers

Handling Query Parameters

Use the params argument to send query parameters in a GET request.

params = {"userId": 1}
response = requests.get("https://jsonplaceholder.typicode.com/posts", params=params)

print(response.url)          # Output: URL with query parameters
print(response.json())       # Filtered JSON data

Sending Headers

Add custom headers to your request.

headers = {"Authorization": "Bearer YOUR_TOKEN_HERE"}
response = requests.get("https://api.example.com/resource", headers=headers)

print(response.status_code)

Error Handling

Check for Errors

Use response.raise_for_status() to raise an exception for HTTP errors.

try:
    response = requests.get("https://jsonplaceholder.typicode.com/invalid-endpoint")
    response.raise_for_status()
except requests.exceptions.HTTPError as e:
    print("HTTP error:", e)
except requests.exceptions.RequestException as e:
    print("Error:", e)

Advanced Topics

Timeout

Set a timeout to avoid hanging requests.

try:
    response = requests.get("https://jsonplaceholder.typicode.com/posts", timeout=5)
    print(response.json())
except requests.exceptions.Timeout:
    print("Request timed out")

Session Objects

Reuse connections with a session object.

session = requests.Session()
session.headers.update({"Authorization": "Bearer YOUR_TOKEN_HERE"})

response = session.get("https://api.example.com/resource")
print(response.json())

Practical Examples

Get Weather Data

api_key = "YOUR_API_KEY"
city = "London"
url = f"http://api.openweathermap.org/data/2.5/weather?q={city}&appid={api_key}"

response = requests.get(url)
if response.status_code == 200:
    weather = response.json()
    print(f"Temperature: {weather['main']['temp']}K")
else:
    print("Failed to fetch weather data")

Search GitHub Repositories

url = "https://api.github.com/search/repositories"
params = {"q": "requests language:python", "sort": "stars"}
response = requests.get(url, params=params)

if response.status_code == 200:
    data = response.json()
    for repo in data["items"][:5]:
        print(repo["name"], "-", repo["html_url"])

Best Practices

Use Environment Variables:
- Store API keys and sensitive data in environment variables instead of hardcoding them.
Handle Errors Gracefully:
- Always check the response status code and handle exceptions.
Rate Limiting:
- Respect API rate limits to avoid being blocked.
Use Secure Connections:
- Always use HTTPS for secure communication.

Practice Exercises

Simple GET Request:
- Fetch posts from https://jsonplaceholder.typicode.com/posts and display the titles.
Weather API:
- Write a program that fetches weather data for a user-specified city.
POST Request:
- Send a POST request to create a new resource and verify the response.
Error Handling:
- Make a request to an invalid endpoint and handle the resulting error.

APIs are a powerful way to interact with external services and exchange data. Understanding how to use the requests library effectively will unlock endless possibilities for building dynamic applications.

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