What is the `warnings` module?

Question

Accepted Answer

**warnings** — alert developers about code issues without raising exceptions.

```python
import warnings

# Issue a warning
def deprecated_function():
    warnings.warn(
        "deprecated_function is deprecated, use new_function instead",
        DeprecationWarning,
        stacklevel=2
    )
    return new_function()

# Control warnings
warnings.filterwarnings("ignore", category=DeprecationWarning)
warnings.filterwarnings("error", category=RuntimeWarning)

# Context manager
with warnings.catch_warnings():
    warnings.simplefilter("ignore")
    deprecated_function()  # No warning shown

# Warning categories
warnings.warn("Default warning", UserWarning)          # default
warnings.warn("Deprecated", DeprecationWarning)        # deprecated API
warnings.warn("Runtime issue", RuntimeWarning)         # runtime
```

**Best practices:**
- Use stacklevel=2 to point to the caller.
- Use specific warning categories.
- Filter warnings in production.

Python: What is the `warnings` module?