diff --git a/doc/devel/contributing.rst b/doc/devel/contributing.rst
index 5140260b3f63..a90dc1694d6a 100644
--- a/doc/devel/contributing.rst
+++ b/doc/devel/contributing.rst
@@ -435,18 +435,22 @@ To include `logging` in your module, at the top of the module, you need to
will log to a logger named ``matplotlib.yourmodulename``.
If an end-user of Matplotlib sets up `logging` to display at levels
-more verbose than `logger.WARNING` in their code as follows::
+more verbose than `logger.WARNING` in their code with the Matplotlib-provided
+helper::
+
+ plt.set_loglevel("debug")
+
+or manually with ::
import logging
- fmt = '%(name)s:%(lineno)5d - %(levelname)s - %(message)s'
- logging.basicConfig(level=logging.DEBUG, format=fmt)
+ logging.basicConfig(level=logging.DEBUG)
import matplotlib.pyplot as plt
Then they will receive messages like::
- matplotlib.backends: 89 - INFO - backend MacOSX version unknown
- matplotlib.yourmodulename: 347 - INFO - Here is some information
- matplotlib.yourmodulename: 348 - DEBUG - Here is some more detailed information
+ DEBUG:matplotlib.backends:backend MacOSX version unknown
+ DEBUG:matplotlib.yourmodulename:Here is some information
+ DEBUG:matplotlib.yourmodulename:Here is some more detailed information
Which logging level to use?
~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/doc/faq/troubleshooting_faq.rst b/doc/faq/troubleshooting_faq.rst
index 7002156948e2..3511a2141271 100644
--- a/doc/faq/troubleshooting_faq.rst
+++ b/doc/faq/troubleshooting_faq.rst
@@ -114,35 +114,18 @@ provide the following information in your e-mail to the `mailing list
the error will help you find a bug in *your* code that is causing the
problem.
-* You can get helpful debugging output from Matlotlib by using the `logging`
- library in your code and posting the verbose output to the lists. For a
- command-line version of this, try::
+* Matplotlib provides debugging information through the `logging` library, and
+ a helper function to set the logging level: one can call ::
- python -c "from logging import *; basicConfig(level=DEBUG); from pylab import *; plot(); show()"
+ plt.set_loglevel("info") # or "debug" for more info
+ to obtain this debugging information.
- If you want to put the debugging hooks in your own code, then the
- most simple way to do so is to insert the following *before* any calls
- to ``import matplotlib``::
-
- import logging
- logging.basicConfig(level=logging.DEBUG)
-
- import matplotlib.pyplot as plt
-
- Note that if you want to use `logging` in your own code, but do not
- want verbose Matplotlib output, you can set the logging level
- for Matplotlib independently::
-
- import logging
- # set DEBUG for everything
- logging.basicConfig(level=logging.DEBUG)
- logger = logging.getLogger('matplotlib')
- # set WARNING for Matplotlib
- logger.setLevel(logging.WARNING)
-
- The `logging` module is very flexible, and can be a valuable tool in chasing
- down errors.
+ Standard functions from the `logging` module are also applicable; e.g. one
+ could call ``logging.basicConfig(level="DEBUG")`` even before importing
+ Matplotlib (this is in particular necessary to get the logging info emitted
+ during Matplotlib's import), or attach a custom handler to the "matplotlib"
+ logger. This may be useful if you use a custom logging configuration.
If you compiled Matplotlib yourself, please also provide:
diff --git a/doc/users/next_whats_new/2019-01-24-AL-set_loglevel.rst b/doc/users/next_whats_new/2019-01-24-AL-set_loglevel.rst
new file mode 100644
index 000000000000..9649ed80f481
--- /dev/null
+++ b/doc/users/next_whats_new/2019-01-24-AL-set_loglevel.rst
@@ -0,0 +1,7 @@
+:orphan:
+
+New logging API
+```````````````
+
+`matplotlib.set_loglevel`/`.pyplot.set_loglevel` can be called to display more
+(or less) detailed logging output.
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
index 97c7fd5f05be..566cc14832aa 100644
--- a/lib/matplotlib/__init__.py
+++ b/lib/matplotlib/__init__.py
@@ -206,48 +206,43 @@ def _check_versions():
sys.argv = ['modpython']
-_verbose_msg = """\
-matplotlib.verbose is deprecated;
-Command line argument --verbose-LEVEL is deprecated.
-This functionality is now provided by the standard
-python logging library. To get more (or less) logging output:
- import logging
- logger = logging.getLogger('matplotlib')
- logger.set_level(logging.INFO)"""
+# The decorator ensures this always returns the same handler (and it is only
+# attached once).
+@functools.lru_cache()
+def _ensure_handler():
+ """
+ The first time this function is called, attach a `StreamHandler` using the
+ same format as `logging.basicConfig` to the Matplotlib root logger.
+
+ Return this handler every time this function is called.
+ """
+ handler = logging.StreamHandler()
+ handler.setFormatter(logging.Formatter(logging.BASIC_FORMAT))
+ _log.addHandler(handler)
+ return handler
-def _set_logger_verbose_level(level_str='silent', file_str='sys.stdout'):
+def set_loglevel(level):
"""
- Use a --verbose-LEVEL level to set the logging level:
+ Sets the Matplotlib's root logger and root logger handler level, creating
+ the handler if it does not exist yet.
+ Typically, one should call ``set_loglevel("info")`` or
+ ``set_loglevel("debug")`` to get additional debugging information.
+
+ Parameters
+ ----------
+ level : {"notset", "debug", "info", "warning", "error", "critical"}
+ The log level of the handler.
+
+ Notes
+ -----
+ The first time this function is called, an additional handler is attached
+ to Matplotlib's root handler; this handler is reused every time and this
+ function simply manipulates the logger and handler's level.
"""
- levelmap = {'silent': logging.WARNING, 'helpful': logging.INFO,
- 'debug': logging.DEBUG, 'debug-annoying': logging.DEBUG,
- 'info': logging.INFO, 'warning': logging.WARNING}
- # Check that current state of logger isn't already more verbose
- # than the requested level. If it is more verbose, then leave more
- # verbose.
- newlev = levelmap[level_str]
- oldlev = _log.getEffectiveLevel()
- if newlev < oldlev:
- _log.setLevel(newlev)
- std = {
- 'sys.stdout': sys.stdout,
- 'sys.stderr': sys.stderr,
- }
- if file_str in std:
- fileo = std[file_str]
- else:
- fileo = sys.stdout
- try:
- fileo = open(file_str, 'w')
- # if this fails, we will just write to stdout
- except IOError:
- _log.warning('could not open log file "{0}" for writing. '
- 'Check your matplotlibrc'.format(file_str))
- console = logging.StreamHandler(fileo)
- console.setLevel(newlev)
- _log.addHandler(console)
+ _log.setLevel(level.upper())
+ _ensure_handler().setLevel(level.upper())
def _logged_cached(fmt, func=None):
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
index 140aa451e0a2..52a2e1322d65 100644
--- a/lib/matplotlib/pyplot.py
+++ b/lib/matplotlib/pyplot.py
@@ -18,6 +18,7 @@
The object-oriented API is recommended for more complex plots.
"""
+import functools
import importlib
import inspect
import logging
@@ -166,6 +167,11 @@ def uninstall_repl_displayhook():
draw_all = _pylab_helpers.Gcf.draw_all
+@functools.wraps(matplotlib.set_loglevel)
+def set_loglevel(*args, **kwargs): # Ensure this appears in the pyplot docs.
+ return matplotlib.set_loglevel(*args, **kwargs)
+
+
@docstring.copy(Artist.findobj)
def findobj(o=None, match=None, include_self=True):
if o is None:
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