Logging and Warnings#

Newton reports diagnostics through two standard Python mechanisms:

  • Log records from the logging module, under the newton logger. These carry verbose=True output, status messages, and problems Newton worked around, such as asset content an importer skipped.

  • Warnings from the warnings module, using the categories in newton.exceptions. These ask you to change how you call Newton, for example to stop using a deprecated feature.

Each mechanism has its own configuration: logger levels do not affect warnings, and warning filters do not affect log records.

Default output#

Until your application configures logging, Newton prints its log records itself:

  • INFO records go to stdout, unchanged.

  • WARNING and higher go to stderr, prefixed with Warning: or Error:.

  • DEBUG records are hidden.

As soon as a handler is attached to the newton logger or to any of its ancestors, including the root logger, Newton stops printing and its records go only to the configured handlers. This happens when your application calls logging.basicConfig(), under pytest’s log capture, and in host applications and frameworks that configure logging themselves.

Controlling log output#

Configure the newton logger with the standard logging API:

import logging

# Hide INFO output, such as verbose=True diagnostics.
logging.getLogger("newton").setLevel(logging.WARNING)

# Or show DEBUG details as well.
logging.getLogger("newton").setLevel(logging.DEBUG)

To change the format or destination, configure handlers as usual. Once you do, Newton no longer prints on its own, so add a console handler if you still want console output:

import logging

logging.basicConfig(level=logging.INFO, format="%(levelname)s %(name)s: %(message)s")
logging.getLogger("newton").addHandler(logging.FileHandler("newton.log"))

Configure the newton logger itself rather than its children. Child logger names follow Newton’s internal module layout and may change between releases.

verbose arguments#

Functions that accept verbose=True, such as add_mjcf() and add_usd(), log their output at INFO; some also report skipped asset content at WARNING only when verbose is set. The newton logger defaults to INFO, so this output is visible unless you raise the logger’s level.

Controlling warnings#

Newton emits deprecations as NewtonDeprecationWarning, a subclass of DeprecationWarning, and all other warnings as NewtonWarning, a subclass of UserWarning. Existing filters for the builtin categories therefore keep matching the same warnings as before. Filter them by category instead of by message:

import warnings

import newton

# Silence Newton warnings other than deprecations.
warnings.filterwarnings("ignore", category=newton.exceptions.NewtonWarning)

# Fail on Newton deprecations, for example in your test suite.
warnings.filterwarnings("error", category=newton.exceptions.NewtonDeprecationWarning)

Warnings are printed to stderr by Python, not through the newton logger. To send them to your logging handlers as well, call logging.captureWarnings(); Python then logs them under the py.warnings logger.

Testing#

Assert Newton log output with assertLogs() on the "newton" logger or with pytest’s caplog fixture, rather than by capturing stdout. Assert warnings with assertWarns() or pytest.warns.

Limitations#

Some diagnostics are printed from inside Warp kernels while they run on the device. This output bypasses both logging and warnings, so it cannot be filtered, redirected, or silenced through either mechanism.