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Working with the Requests Library

The requests library lets Python programs send HTTP requests to web servers and APIs, making it easy to fetch data from the internet.

What is the Requests Library?

requests is a third-party Python library that simplifies making HTTP calls (GET, POST, PUT, DELETE) to web servers and APIs. It is installed via pip install requests.

Making a GET Request

A GET request retrieves data from a server. The response object contains the status code, headers, and body.

Working with JSON

Most modern APIs return data in JSON format. The .json() method on a response converts the JSON body directly into a Python dictionary or list.

Status Codes

HTTP status codes tell you whether a request succeeded: 200 (OK), 201 (Created), 400 (Bad Request), 401 (Unauthorized), 404 (Not Found), 500 (Server Error). Always check response.status_code or use response.raise_for_status().

Query Parameters and Headers

You can pass query parameters with the params argument and custom headers (such as API keys or authentication tokens) with the headers argument.

POST Requests

POST requests send data to a server, typically to create a resource. Use the json or data argument to send a request body.

Timeouts and Error Handling

Always set a timeout to avoid hanging forever, and wrap requests in try/except to catch requests.exceptions.RequestException.

Syntax

<pre><code>import requests

# GET request
response = requests.get("https://api.example.com/users", timeout=5)
print(response.status_code)   # 200
data = response.json()        # parse JSON body
print(data)

# GET with query parameters
params = {"page": 1, "limit": 10}
response = requests.get("https://api.example.com/items", params=params)

# GET with headers (e.g. API key)
headers = {"Authorization": "Bearer YOUR_API_KEY"}
response = requests.get("https://api.example.com/profile", headers=headers)

# POST request with JSON body
payload = {"name": "Alice", "age": 30}
response = requests.post("https://api.example.com/users", json=payload)

# Error handling
try:
    response = requests.get("https://api.example.com/data", timeout=5)
    response.raise_for_status()
    data = response.json()
except requests.exceptions.RequestException as e:
    print(f"Request failed: {e}")
</code></pre>

Revision Notes

• pip install requests to use this library
• requests.get() / requests.post() for HTTP calls
• response.status_code to check success/failure
• response.json() converts JSON response to dict/list
• params= for query strings, headers= for auth tokens
• Always use timeout= and handle exceptions

Parse a JSON API Response

Medium

You are given a Python dictionary representing a JSON API response with a list of users under the key "users", where each user has "name" and "active" keys. Write a function active_user_names(data) that returns a list of names of users where active is True.

Input:

{"users": [{"name": "Alice", "active": True}, {"name": "Bob", "active": False}, {"name": "Carl", "active": True}]}

Output:

['Alice', 'Carl']

Show Hint

Use a list comprehension iterating over data["users"], filtering where user["active"] is True, and extracting user["name"].

Solve this Challenge

Show Solution

def active_user_names(data):
    return [user["name"] for user in data["users"] if user["active"]]

data = {"users": [{"name": "Alice", "active": True}, {"name": "Bob", "active": False}, {"name": "Carl", "active": True}]}
print(active_user_names(data))

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