Requests

Requests are messages sent by a client to a server to obtain a resource or instruct the server to perform an action. The most common protocol for web requests is HTTP. An HTTP request consists of a request line with a method, a request-target (URL), and the HTTP version; followed by headers, a blank line, and an optional body. Methods indicate the action; GET retrieves data, POST submits data, PUT and PATCH modify resources, DELETE removes them, while HEAD and OPTIONS query metadata. Requests include a Host header and may carry authentication tokens, content types, and other metadata. The body is used when sending data, such as form submissions or JSON.

Upon receiving a request, a server responds with a status code, a reason phrase, and response headers, plus an optional body. Status codes are grouped into classes: 1xx informational, 2xx success, 3xx redirection, 4xx client errors, and 5xx server errors. Headers convey metadata such as content type, length, caching directives, and authentication status. HTTPS, HTTP over TLS, provides encryption and integrity protections for requests and responses.

The requests library is a popular open-source HTTP client for Python. The library offers a high-level API with functions like requests.get, requests.post, and requests.put, and supports sessions, cookies, redirects, streaming responses, timeouts, and automatic handling of JSON data. It aims to be concise and human-friendly and builds on lower-level libraries such as urllib3. Requests is commonly used for interacting with web services, APIs, and web scraping, when allowed by terms of service and robots.txt.

Related concepts include client-side request APIs in web browsers, such as the Fetch API and XMLHttpRequest in JavaScript, and other language-specific HTTP clients. Understanding requests involves considerations of security (TLS, authentication), performance (connection pooling, streaming), and correctness (idempotence, proper method usage).