Logging is important no matter what application you’re writing or what language you’re working in. While Python does offer the logging library, it doesn’t really suit large-scale applications that use services like Datadog or Loki.
Structlog is a library that takes logging and makes your logs structured so that they’re machine-readable. Instead of emitting a flat string:
INFO:root:User 42 checked out order 9981The library instead will write it as a dictionary with appropriate key-value pairs:
{
"event": "checkout_completed",
"user_id": 42,
"order_id": 9981,
"timestamp": "2025-06-23T14:22:01Z",
"level": "info"
}The benefits of using structlog
This package is beneficial for many reasons, with the most obvious being that applications like CloudWatch can index and query it easily; you can throw an LLM at it as well and have it write appropriate grep / find statements and have it do further analysis as well.
However, something that is more powerful is context binding, where you are able to attach shared context (such as a request ID) and it’ll show up on every log line that follows:
import structlog
log = structlog.get_logger()
def handle_request(request_id: str, user_id: int):
bound_log = log.bind(
request_id=request_id,
user_id=user_id
)
bound_log.info("request_started")
# do things
bound_log.info("request_completed", duration_ms=142)Which will give us the following output (formatted to fit on screen):
{
"event": "request_started",
"request_id": "abc-123",
"user_id": 99
}
{
"event": "request_completed",
"request_id": "abc-123",
"user_id": 99,
"duration_ms": 142
}That request_id follows every log line without you having to pass it around manually and remembering to include it.
When should you use it?
If you're writing a quick script that runs once and exits, structlog is overkill. Stick with print() or basic logging.
But if any of these apply to your project, it's worth setting up:
You're running a web service (FastAPI, Flask, Django) and need to trace requests
You're shipping logs to a centralized platform (Datadog, Loki, CloudWatch, Splunk)
You're debugging issues that span multiple services or workers
You need to audit what happened for a specific user or transaction
It also plays well with Python's built-in logging module - you can wire them together so existing libraries that use logging still get their output captured alongside your structlog events.
If you want to go deeper, the official getting started guide is genuinely good and covers processors, async support, and testing.
Happy coding!
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