Python / Uvicorn Fundamentals Interview Questions
What are Uvicorn's default host, port, and log level settings?
Uvicorn's defaults are chosen to be safe for local development - binding only to localhost prevents accidental external exposure, while the info log level provides useful startup and access log output without being overwhelming.
| Setting | Default value | Notes |
|---|---|---|
| --host | 127.0.0.1 | Loopback only - not reachable from other machines |
| --port | 8000 | Standard development port |
| --log-level | info | Options: critical, error, warning, info, debug, trace |
| --workers | 1 | Single process - use WEB_CONCURRENCY env var or --workers for more |
| --loop | auto | Prefers uvloop if installed, falls back to asyncio |
| --http | auto | Prefers httptools if installed, falls back to h11 |
| --ws | auto | Prefers websockets if installed, falls back to wsproto |
| --lifespan | auto | Enables lifespan if supported by the application |
| --proxy-headers | enabled | Trusts X-Forwarded-* headers from 127.0.0.1 |
# To make the server externally accessible (development/testing): uvicorn main:app --host 0.0.0.0 # Production: always specify host explicitly uvicorn main:app --host 0.0.0.0 --port 8000 # Check what's running: curl http://127.0.0.1:8000/ # The WEB_CONCURRENCY environment variable sets default worker count export WEB_CONCURRENCY=4 uvicorn main:app # will start 4 workers
What is Uvicorn's default host binding?
What is Uvicorn's default port?
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