APIs

12. APIs#

APIs let your code communicate with web services, data sources, and cloud tools.

REST APIs and HTTP methods
requests.get() and response objects
JSON data as Python dictionaries and lists
Query parameters and headers
Reliability patterns for errors, timeouts, pagination, and retries

Chapter Video

This overview introduces HTTP requests in Python, including reading JSON data from web responses.

Python Requests Tutorial: Request Web Pages, Download Images, POST Data, Read JSON, and More (25:00) by Corey Schafer

Hosted on YouTube; property of its original creator, embedded here for educational reference only.

Learning Objectives

By the end of this chapter, you will be able to:

Explain what an API is and how REST APIs communicate over HTTP
Make GET requests with requests, pass query parameters, and convert between JSON text and Python objects with response.json(), json.loads(), and json.dumps()
Handle HTTP errors, timeouts, and invalid JSON without crashing your program
Send POST requests with JSON bodies and authenticate with headers and API keys read from environment variables
Parse nested JSON defensively and validate a response against the keys your code expects
Collect paginated results and retry temporary failures with exponential backoff

Chapter Flow

Glossary

#	Term	Explanation
1	API	An application programming interface, a defined way for software systems to communicate.
2	Web API	An API accessed over the web, usually with HTTP requests.
3	HTTP	The protocol commonly used for web requests and responses.
4	REST	An API design style that uses resources, URLs, and standard HTTP methods.
5	Endpoint	A URL where a specific API resource or action is available.
6	HTTP method	A request action such as GET, POST, PUT, PATCH, or DELETE.
7	Status code	A numeric response code that summarizes whether an HTTP request succeeded or failed.
8	GET request	An HTTP request used to retrieve data.
9	POST request	An HTTP request commonly used to send new data to a server.
10	Query parameter	A key-value option added to a URL to customize a request.
11	URL encoding	Replacing special characters in a URL, such as spaces, `&`, and `=`, with `%` codes so values cannot break the query string.
12	Header	Metadata sent with an HTTP request or response.
13	API key	A credential used to identify or authorize an API client.
14	JSON	A text data format commonly used for API request and response bodies.
15	JSON serialization	Converting Python objects to JSON text with `json.dumps()`; `json.loads()` parses JSON text back into Python objects.
16	Response body	The data returned by a server after a request.
17	`requests`	A popular Python library for making HTTP requests.
18	Timeout	A limit on how long a client waits for a response.
19	Pagination	Splitting a large API response into multiple pages or batches.
20	Exponential backoff	A retry strategy that increases wait time after repeated transient failures.
21	Retry	Trying a failed request again, often after a short delay.
22	Response contract	The expected structure and meaning of data returned by an API.
23	Environment variable	A named value set outside the program, read in Python with `os.environ.get()`, often used to keep secrets out of source code.
24	Authorization header	The HTTP header that carries a client’s credentials, such as an API token, with each request.
25	Bearer token	An access token sent as `Authorization: Bearer <token>`, granting access to whoever presents it.
26	Prepared request	A request that `requests` has fully built, including its final URL and headers, but has not yet sent.
27	Cursor-based pagination	A pagination scheme in which each response returns a token, such as `next_cursor`, that names the next page to request.
28	Jitter	A small random amount added to a retry delay so that many clients do not retry at exactly the same time.
29	`RequestException`	The base class of the `requests` exceptions, so `except requests.RequestException` catches any request failure.