Environment:Anthropics Anthropic sdk python Python SDK Core Environment

Knowledge Sources	anthropic-sdk-python PyPI anthropic
Domains	Infrastructure, API_Client
Last Updated	2026-02-15 12:00 GMT

Overview

Python >= 3.9 environment with httpx, pydantic, anyio, and supporting libraries for the Anthropic Python SDK (v0.79.0).

Description

This environment provides the core runtime for interacting with the Anthropic Messages API. It requires Python 3.9 or later and a set of mandatory dependencies including httpx for HTTP transport, pydantic (v1 or v2) for response modeling, anyio for async compatibility, and jiter for fast JSON parsing. The SDK supports both synchronous and asynchronous usage patterns across all major operating systems (Linux, macOS, Windows).

Usage

Use this environment for any workflow involving the Anthropic Python SDK, including basic message conversations, streaming, tool use, structured output extraction, extended thinking, and cloud provider integrations. This is the mandatory base environment for all SDK operations.

System Requirements

Category	Requirement	Notes
OS	Linux, macOS, Windows	OS-independent; POSIX preferred
Python	>= 3.9	Supports 3.9, 3.10, 3.11, 3.12, 3.13, 3.14
Network	HTTPS outbound to api.anthropic.com	Port 443; configurable via ANTHROPIC_BASE_URL

Dependencies

Python Packages (Required)

httpx >= 0.25.0, < 1
pydantic >= 1.9.0, < 3
typing-extensions >= 4.10, < 5
anyio >= 3.5.0, < 5
distro >= 1.7.0, < 2
sniffio
jiter >= 0.4.0, < 1
docstring-parser >= 0.15, < 1

Python Packages (Optional)

aiohttp + httpx_aiohttp >= 0.1.9 (for improved async concurrency)

Credentials

The following environment variables are used for authentication:

ANTHROPIC_API_KEY: Primary API key for authenticating with the Anthropic API.
ANTHROPIC_AUTH_TOKEN: Alternative bearer token authentication (mutually exclusive with API key).
ANTHROPIC_BASE_URL: Override the default API base URL (defaults to https://api.anthropic.com).
ANTHROPIC_LOG: Controls SDK logging level. Set to "debug" or "info" for diagnostics.
DEFER_PYDANTIC_BUILD: Controls Pydantic model building timing (defaults to "true").

Quick Install

pip install anthropic

For optional aiohttp support:

pip install 'anthropic[aiohttp]'

Code Evidence

Dependency declarations from pyproject.toml:11-19:

dependencies = [
    "httpx>=0.25.0, <1",
    "pydantic>=1.9.0, <3",
    "typing-extensions>=4.10, <5",
    "anyio>=3.5.0, <5",
    "distro>=1.7.0, <2",
    "sniffio",
    "jiter>=0.4.0, <1",
    "docstring-parser>=0.15,<1",
]

Python version requirement from pyproject.toml:22:

requires-python = ">= 3.9"

Environment variable handling from _client.py:92-103:

if api_key is None:
    api_key = os.environ.get("ANTHROPIC_API_KEY")
self.api_key = api_key

if auth_token is None:
    auth_token = os.environ.get("ANTHROPIC_AUTH_TOKEN")
self.auth_token = auth_token

if base_url is None:
    base_url = os.environ.get("ANTHROPIC_BASE_URL")
if base_url is None:
    base_url = f"https://api.anthropic.com"

Common Errors

Error Message	Cause	Solution
`AuthenticationError` (401)	Missing or invalid API key	Set `ANTHROPIC_API_KEY` environment variable or pass `api_key` parameter
`RateLimitError` (429)	Too many requests	SDK auto-retries with backoff; reduce request rate if persistent
`ValueError: Streaming is required for operations that may take longer than 10 minutes`	Non-streaming request with high max_tokens	Use `stream=True` or reduce `max_tokens`
`MissingDependencyError`	Optional extra not installed	Run `pip install anthropic[vertex]` or `anthropic[bedrock]`

Compatibility Notes

Pydantic v1 and v2: The SDK includes a compatibility layer (_compat.py) that supports both Pydantic v1 (1.9.0+) and v2 (2.x). Method dispatch is performed at runtime.
Async Runtimes: Supports asyncio and other async runtimes via anyio. The sniffio library detects the active async library.
HTTP Client: Default is httpx; optional aiohttp backend via httpx_aiohttp for improved async concurrency.
Python 3.14: Supported per pyproject.toml classifiers.

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