logging.md

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# Logging

🤗 Transformers has a centralized logging system, so that you can setup the verbosity of the library easily.

Currently the default verbosity of the library is `WARNING`.

To change the level of verbosity, just use one of the direct setters. For instance, here is how to change the verbosity
to the INFO level.

```python
import transformers

transformers.logging.set_verbosity_info()
```

You can also use the environment variable `TRANSFORMERS_VERBOSITY` to override the default verbosity. You can set it
to one of the following: `debug`, `info`, `warning`, `error`, `critical`. For example:

```bash
TRANSFORMERS_VERBOSITY=error ./myprogram.py
```

Additionally, some `warnings` can be disabled by setting the environment variable
`TRANSFORMERS_NO_ADVISORY_WARNINGS` to a true value, like *1*. This will disable any warning that is logged using
[`logger.warning_advice`]. For example:

```bash
TRANSFORMERS_NO_ADVISORY_WARNINGS=1 ./myprogram.py
```

Here is an example of how to use the same logger as the library in your own module or script:

```python
from transformers.utils import logging

logging.set_verbosity_info()
logger = logging.get_logger("transformers")
logger.info("INFO")
logger.warning("WARN")
```


All the methods of this logging module are documented below, the main ones are
[`logging.get_verbosity`] to get the current level of verbosity in the logger and
[`logging.set_verbosity`] to set the verbosity to the level of your choice. In order (from the least
verbose to the most verbose), those levels (with their corresponding int values in parenthesis) are:

- `transformers.logging.CRITICAL` or `transformers.logging.FATAL` (int value, 50): only report the most
  critical errors.
- `transformers.logging.ERROR` (int value, 40): only report errors.
- `transformers.logging.WARNING` or `transformers.logging.WARN` (int value, 30): only reports error and
  warnings. This the default level used by the library.
- `transformers.logging.INFO` (int value, 20): reports error, warnings and basic information.
- `transformers.logging.DEBUG` (int value, 10): report all information.

By default, `tqdm` progress bars will be displayed during model download. [`logging.disable_progress_bar`] and [`logging.enable_progress_bar`] can be used to suppress or unsuppress this behavior.

## `logging` vs `warnings`

Python has two logging systems that are often used in conjunction: `logging`, which is explained above, and `warnings`,
which allows further classification of warnings in specific buckets, e.g., `FutureWarning` for a feature or path
that has already been deprecated and `DeprecationWarning` to indicate an upcoming deprecation.

We use both in the `transformers` library. We leverage and adapt `logging`'s `captureWarning` method to allow
management of these warning messages by the verbosity setters above.

What does that mean for developers of the library? We should respect the following heuristic:
- `warnings` should be favored for developers of the library and libraries dependent on `transformers`
- `logging` should be used for end-users of the library using it in every-day projects

See reference of the `captureWarnings` method below.

[[autodoc]] logging.captureWarnings

## Base setters

[[autodoc]] logging.set_verbosity_error

[[autodoc]] logging.set_verbosity_warning

[[autodoc]] logging.set_verbosity_info

[[autodoc]] logging.set_verbosity_debug

## Other functions

[[autodoc]] logging.get_verbosity

[[autodoc]] logging.set_verbosity

[[autodoc]] logging.get_logger

[[autodoc]] logging.enable_default_handler

[[autodoc]] logging.disable_default_handler

[[autodoc]] logging.enable_explicit_format

[[autodoc]] logging.reset_format

[[autodoc]] logging.enable_progress_bar

[[autodoc]] logging.disable_progress_bar