# 14.2.6. Setting up logging — `MDAnalysis.lib.log`

Configure logging for MDAnalysis. Import this module if logging is desired in application code.

Logging to a file and the console is set up by default as described under logging to multiple destinations.

The top level logger of the library is named MDAnalysis by convention; a simple logger that writes to the console and logfile can be created with the `create()` function. This only has to be done once. For convenience, the default MDAnalysis logger can be created with `MDAnalysis.start_logging()`:

    import MDAnalysis
    MDAnalysis.start_logging()

Once this has been done, MDAnalysis will write messages to the logfile (named MDAnalysis.log by default but this can be changed with the optional argument to `start_logging()`).

Any code can log to the MDAnalysis logger by using

    import logging
    logger = logging.getLogger('MDAnalysis.MODULENAME')

    # use the logger, for example at info level:
    logger.info("Starting task ...")

The important point is that the name of the logger begins with “MDAnalysis.”.

Note

The `logging` module in the standard library contains in depth documentation about using logging.

## 14.2.6.1. Convenience functions

Two convenience functions at the top level make it easy to start and stop the default MDAnalysis logger.

MDAnalysis.start_logging(logfile='MDAnalysis.log', version='2.10.0')

  Start logging of messages to file and console.

  The default logfile is named MDAnalysis.log and messages are logged with the tag MDAnalysis.

MDAnalysis.stop_logging()

  Stop logging to logfile and console.

## 14.2.6.2. Other functions and classes for logging purposes

Changed in version 2.0.0: Deprecated `MDAnalysis.lib.log.ProgressMeter` has now been removed.

class MDAnalysis.lib.log.NullHandler(level=0)

  Silent Handler.

  Useful as a default:

      h = NullHandler()
      logging.getLogger("MDAnalysis").addHandler(h)
      del h

  see the advice on logging and libraries in http://docs.python.org/library/logging.html?#configuring-logging-for-a-library

  Initializes the instance - basically setting the formatter to None and the filter list to empty.

  emit(record)

    Do whatever it takes to actually log the specified logging record.

    This version is intended to be implemented by subclasses and so raises a NotImplementedError.

class MDAnalysis.lib.log.ProgressBar(*_, **__)

  Display a visual progress bar and time estimate.

  The `ProgressBar` decorates an iterable object, returning an iterator which acts exactly like the original iterable, but prints a dynamically updating progressbar every time a value is requested. See the example below for how to use it when iterating over the frames of a trajectory.

  Parameters:

    - iterable (iterable, optional) – Iterable to decorate with a progressbar. Leave blank to manually manage the updates.

    - verbose (bool, optional) – If `True` (the default) then show the progress bar, unless the disable keyword is set to `True` (disable takes precedence over verbose). If verbose is set to `None` then the progress bar is displayed (like `True`), unless this is a non-TTY output device (see disable).

    - desc (str, optional) – Prefix for the progressbar.

    - total (int or float, optional) – The number of expected iterations. If unspecified, `len(iterable)` is used if possible. If `float("inf")` or as a last resort, only basic progress statistics are displayed (no ETA, no progressbar).

    - leave (bool, optional) – If [default: `True`], keeps all traces of the progressbar upon termination of iteration. If `None`, will leave only if position is 0.

    - file (`io.TextIOWrapper` or `io.StringIO`, optional) – Specifies where to output the progress messages (default: `sys.stderr`). Uses `file.write()` and `file.flush()` methods. For encoding, see write_bytes.

    - ncols (int, optional) – The width of the entire output message. If specified, dynamically resizes the progressbar to stay within this bound. If unspecified, attempts to use environment width. The fallback is a meter width of 10 and no limit for the counter and statistics. If 0, will not print any meter (only stats).

    - mininterval (float, optional) – Minimum progress display update interval [default: 0.1] seconds.

    - maxinterval (float, optional) – Maximum progress display update interval [default: 10] seconds. Automatically adjusts miniters to correspond to mininterval after long display update lag. Only works if dynamic_miniters or monitor thread is enabled.

    - miniters (int or float, optional) – Minimum progress display update interval, in iterations. If 0 and dynamic_miniters, will automatically adjust to equal mininterval (more CPU efficient, good for tight loops). If > 0, will skip display of specified number of iterations. Tweak this and mininterval to get very efficient loops. If your progress is erratic with both fast and slow iterations (network, skipping items, etc) you should set miniters=1.

    - ascii (bool or str, optional) – If unspecified or `False`, use unicode (smooth blocks) to fill the meter. The fallback is to use ASCII characters “ 123456789#”.

    - disable (bool, optional) – Whether to disable the entire progressbar wrapper [default: `False`]. If set to None, disable on non-TTY.

    - unit (str, optional) – String that will be used to define the unit of each iteration [default: it].

    - unit_scale (bool or int or float, optional) – If 1 or True, the number of iterations will be reduced/scaled automatically and a metric prefix following the International System of Units standard will be added (kilo, mega, etc.) [default: `False`]. If any other non-zero number, will scale total and n.

    - dynamic_ncols (bool, optional) – If set, constantly alters ncols and nrows to the environment (allowing for window resizes) [default: `False`].

    - smoothing (float, optional) – Exponential moving average smoothing factor for speed estimates (ignored in GUI mode). Ranges from 0 (average speed) to 1 (current/instantaneous speed) [default: 0.3].

    - bar_format (str, optional) –

      Specify a custom bar string formatting. May impact performance. [default: `'{l_bar}{bar}{r_bar}'`], where `l_bar='{desc}: {percentage:3.0f}%|'` and `r_bar='| {n_fmt}/{total_fmt} [{elapsed}<{remaining}, {rate_fmt}{postfix}]'`

      Possible vars: l_bar, bar, r_bar, n, n_fmt, total, total_fmt, percentage, elapsed, elapsed_s, ncols, nrows, desc, unit, rate, rate_fmt, rate_noinv, rate_noinv_fmt, rate_inv, rate_inv_fmt, postfix, unit_divisor, remaining, remaining_s.

      Note that a trailing “: “ is automatically removed after {desc} if the latter is empty.

    - initial (int or float, optional) – The initial counter value. Useful when restarting a progress bar [default: 0]. If using `float`, consider specifying `{n:.3f}` or similar in bar_format, or specifying unit_scale.

    - position (int, optional) – Specify the line offset to print this bar (starting from 0) Automatic if unspecified. Useful to manage multiple bars at once (e.g., from threads).

    - postfix (dict or *, optional) – Specify additional stats to display at the end of the bar. Calls `set_postfix(**postfix)` if possible (`dict`).

    - unit_divisor (float, optional) – [default: 1000], ignored unless unit_scale is `True`.

    - write_bytes (bool, optional) – If (default: `None`) and file is unspecified, bytes will be written in Python 2. If True will also write bytes. In all other cases will default to unicode.

    - lock_args (tuple, optional) – Passed to refresh for intermediate output (initialisation, iterating, and updating).

    - nrows (int, optional) – The screen height. If specified, hides nested bars outside this bound. If unspecified, attempts to use environment height. The fallback is 20.

  Returns:

    out

  Return type:

    decorated iterator.

  Example

  To get a progress bar when analyzing a trajectory:

      from MDAnalysis.lib.log import ProgressBar

      ...

      for ts in ProgressBar(u.trajectory):
         # perform analysis

  will produce something similar to

      30%|███████████                       | 3/10 [00:13<00:30,  4.42s/it]

  in a terminal or Jupyter notebook.

  See also

  The `ProgressBar` is derived from `tqdm.auto.tqdm`; see the tqdm documentation for further details on how to use it.

MDAnalysis.lib.log.clear_handlers(logger)

  clean out handlers in the library top level logger

  (only important for reload/debug cycles…)

MDAnalysis.lib.log.create(logger_name='MDAnalysis', logfile='MDAnalysis.log')

  Create a top level logger.

  - The file logger logs everything (including DEBUG).

  - The console logger only logs INFO and above.

  Logging to a file and the console as described under logging to multiple destinations.

  The top level logger of MDAnalysis is named MDAnalysis. Note that we are configuring this logger with console output. If a root logger also does this then we will get two output lines to the console.

MDAnalysis.lib.log.start_logging(logfile='MDAnalysis.log', version='2.10.0')

  Start logging of messages to file and console.

  The default logfile is named MDAnalysis.log and messages are logged with the tag MDAnalysis.

MDAnalysis.lib.log.stop_logging()

  Stop logging to logfile and console.