<!--
title: Explicit None Checks
domain: ai-agents
topic: Null Handling
language: Python
source: anthropics/anthropic-sdk-python
updated: 2026-02-09
url: https://awesomereviewers.com/reviewers/anthropic-sdk-python-explicit-none-checks/
-->

When working with nullable/optional values, treat `None` (absence) differently from other falsy values like `""` (empty string) or `0` (zero). Use explicit `is not None` checks when empty values are valid, and avoid repeating null checks after you’ve already established a non-null invariant via an early return/guard.

Apply it like this:
- Prefer `if x is not None:` over `if x:` when `x` may be an empty string/zero but should still be considered “present”.
- After an early return for `None`, don’t add redundant `x is not None` guards later.

Example:
```python
import os

bearer = os.getenv("AWS_BEARER_TOKEN_BEDROCK")
# Empty string is a valid value, so check for None (absence), not truthiness.
if bearer is not None:
    headers["Authorization"] = f"Bearer {bearer}"

# Later, avoid redundant None checks after a guard/early return:
if response is None:
    return
if response.get("content"):
    append_messages(message, response)
```