API Changes for 3.1.0
=====================

.. contents::
   :local:
   :depth: 1


Behavior changes
----------------


Matplotlib.use
~~~~~~~~~~~~~~
Switching backends via `matplotlib.use` is now allowed by default,
regardless of whether `matplotlib.pyplot` has been imported. If the user
tries to switch from an already-started interactive backend to a different
interactive backend, an `ImportError` will be raised.

mplot3d auto-registration
~~~~~~~~~~~~~~~~~~~~~~~~~

`mpl_toolkits.mplot3d` is always registered by default now. It is no
longer necessary to import mplot3d to create 3d axes with ::

  ax = fig.add_subplot(111, projection="3d")

Invalid points in PathCollections
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PathCollections created with `~.Axes.scatter` now keep track of invalid points.
Previously, points with nonfinite (infinite or nan) coordinates would not be
included in the offsets (as returned by `PathCollection.get_offsets`) of a
`PathCollection` created by `~.Axes.scatter`, and points with nonfinite values
(as specified by the *c* kwarg) would not be included in the array (as returned
by `PathCollection.get_array`)

Such points are now included, but masked out by returning a masked array.

If the *plotnonfinite* kwarg to `~.Axes.scatter` is set, then points
with nonfinite values are plotted using the bad color of the
`.collections.PathCollection`\ 's colormap (as set by
:meth:`.colors.Colormap.set_bad`).

Alpha blending in imshow of RBGA input
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The alpha-channel of RBGA images is now re-sampled independently of
RGB channels.  While this is a bug fix, it does change the output and
may result in some down-stream image comparison tests to fail.

Autoscaling
~~~~~~~~~~~
On log-axes where a single value is plotted at a "full" decade (1, 10, 100,
etc.), the autoscaling now expands the axis symmetrically around that point,
instead of adding a decade only to the right.

Log-scaled axes
~~~~~~~~~~~~~~~
When the default `LogLocator` would generate no ticks for an axis (e.g., an
axis with limits from 0.31 to 0.39) or only a single tick, it now instead falls
back on the linear `AutoLocator` to pick reasonable tick positions.

`.Figure.add_subplot` with no arguments
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Calling `.Figure.add_subplot()` with no positional arguments used to do
nothing; this now is equivalent to calling ``add_subplot(111)`` instead.

`~.Axes.bxp` and rcparams
~~~~~~~~~~~~~~~~~~~~~~~~~
`~.Axes.bxp` now respects :rc:`boxplot.boxprops.linewidth` even when
*patch_artist* is set.
Previously, when the *patch_artist* parameter was set, `~.Axes.bxp` would ignore
:rc:`boxplot.boxprops.linewidth`.  This was an oversight -- in particular,
`~.Axes.boxplot` did not ignore it.

Major/minor tick collisions
~~~~~~~~~~~~~~~~~~~~~~~~~~~

Minor ticks that collide with major ticks are now hidden by default.
Previously, certain locator classes (`~.ticker.LogLocator`,
`~.ticker.AutoMinorLocator`) contained custom logic to avoid emitting
tick locations that collided with major ticks when they were used as
minor locators.  This logic has now moved to the `~.axis.Axis` class,
and is used regardless of the locator class.  You can control this
behavior via the `~.Axis.remove_overlaping_locs` attribute on
`~.axis.Axis`.

If you were relying on both the major and minor tick labels to appear
on the same tick, you may need to update your code.  For example, the
following snippet ::

    import numpy as np
    import matplotlib.dates as mdates
    import matplotlib.pyplot as plt

    t = np.arange("2018-11-03", "2018-11-06", dtype="datetime64")
    x = np.random.rand(len(t))

    fig, ax = plt.subplots()
    ax.plot(t, x)
    ax.xaxis.set(
        major_locator=mdates.DayLocator(),
        major_formatter=mdates.DateFormatter("\n%a"),
        minor_locator=mdates.HourLocator((0, 6, 12, 18)),
        minor_formatter=mdates.DateFormatter("%H:%M"),
    )
    # disable removing overlapping locations
    ax.xaxis.remove_overlapping_locs = False
    plt.show()

labeled days using major ticks, and hours and minutes using minor
ticks and added a newline to the major ticks labels to avoid them
crashing into the minor tick labels.  Setting the
`~.Axis.remove_overlapping_locs` property (also accessible via
`~.Axis.set_remove_overlapping_locs` /
`~.Axis.get_remove_overlapping_locs` and `~.pyplot.setp`) disables
removing overlapping tick locations.

The major tick labels could also be adjusted include hours and
minutes, as the minor ticks are gone, so the ``major_formatter``
would be::

  mdates.DateFormatter("%H:%M\n%a")

usetex support
~~~~~~~~~~~~~~
Previously, if :rc:`text.usetex` was True, then constructing a `TextPath` on
a non-mathtext string with ``usetex=False`` would rely on the mathtext parser
(but not on usetex support!) to parse the string.  The mathtext parser is not
invoked anymore, which may cause slight changes in glyph positioning.

get_window_extents
~~~~~~~~~~~~~~~~~~

`.matplotlib.axes.Axes.get_window_extent` used to return a bounding box
that was slightly larger than the axes, presumably to take into account
the ticks that may be on a spine.  However, it was not scaling the tick sizes
according to the dpi of the canvas, and it did not check if the ticks were
visible, or on the spine.

Now  `.matplotlib.axes.Axes.get_window_extent` just returns the axes extent
with no padding for ticks.

This affects `.matplotlib.axes.Axes.get_tightbbox` in cases where there are
outward ticks with no tick labels, and it also removes the (small) pad around
axes in that case.

`.spines.Spine.get_window_extent` now takes into account ticks that are on the
spine.

Sankey
~~~~~~
Previously, `.Sankey.add` would only accept a single string as the *labels*
argument if its length is equal to the number of flows, in which case it would
use one character of the string for each flow.

The behavior has been changed to match the documented one: when a single string
is passed, it is used to label all the flows.

`~.font_manager.FontManager` scores
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

`.font_manager.FontManager.score_weight` is now more strict with its
inputs.  Previously, when a weight string was passed to
`.font_manager.FontManager.score_weight`,

- if the weight was the string representation of an integer, it would be
  converted to that integer,
- otherwise, if the weight was not a standard weight name, it would be silently
  replaced by a value of 500 ("normal" weight).

`.font_manager.FontManager.score_weight` now raises an exception on such inputs.

Text alignment
~~~~~~~~~~~~~~

Text alignment was previously incorrect, in particular for multiline text
objects with large descenders (i.e. subscripts) and rotated text.  These have
been fixed and made more consistent, but could make old code that has
compensated for this no longer have the correct alignment.

Upper case color strings
~~~~~~~~~~~~~~~~~~~~~~~~

Support for passing single-letter colors (one of "rgbcmykw") as UPPERCASE
characters is deprecated; these colors will become case-sensitive (lowercase)
after the deprecation period has passed.

The goal is to decrease the number of ambiguous cases when using the ``data``
keyword to plotting methods; e.g. ``plot("X", "Y", data={"X": ..., "Y": ...})``
will not warn about "Y" possibly being a color anymore after the deprecation
period has passed.

Degenerate limits
~~~~~~~~~~~~~~~~~

When bounds passed to `~.axes.Axes.set_xlim` are degenerate (i.e. the
lower and upper value are equal), the method used to "expand" the
bounds now matches the expansion behavior of autoscaling when the plot
contains a single x-value, and should in particular produce nicer
limits for non-linear scales.

`~.Axes.plot` format string parsing
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In certain cases, `~.Axes.plot` would previously accept format strings
specifying more than one linestyle (e.g. ``"---."`` which specifies both
``"--"`` and ``"-."``); only use one of them would be used. This now raises a
`ValueError` instead.

HTMLWriter
~~~~~~~~~~
The HTMLWriter constructor is more strict: it no longer normalizes unknown
values of *default_mode* to 'loop', but errors out instead.

AFM parsing
~~~~~~~~~~~
In accordance with the AFM spec, the AFM parser no longer truncates the
``UnderlinePosition`` and ``UnderlineThickness`` fields to integers.

The ``Notice`` field (which can only be publicly accessed by the deprecated
``afm.parse_afm`` API) is no longer decoded to a `str`, but instead kept as
`bytes`, to support non-conformant AFM files that use non-ASCII characters in
that field.

`.Artist.set` keyword normalisation
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
`.Artist.set` now normalizes keywords before sorting them. Previously it sorted
its keyword arguments in reverse alphabetical order (with a special-case to
put ``color`` at the end) before applying them.

It now normalizes aliases (and, as above, emits a warning on duplicate
properties) before doing the sorting (so ``c`` goes to the end too).

`.Axes.tick_params` argument checking
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Previously `.Axes.tick_params` silently did nothing when an invalid *axis*
parameter was supplied. This behavior has been changed to raise a `ValueError`
instead.

`.Axes.hist` output
~~~~~~~~~~~~~~~~~~~

Input that consists of multiple empty lists will now return a list of histogram
values for each one of the lists. For example, an input of ``[[],[]]`` will
return 2 lists of histogram values. Previously, a single list was returned.

`.backend_bases.Timer.remove_callback` future signature change
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Currently, `.backend_bases.Timer.remove_callback(func, *args,
**kwargs)` removes a callback previously added by
`.backend_bases.Timer.add_callback(func, *args, **kwargs)`, but if
``*args, **kwargs`` is not passed in (ex,
``Timer.remove_callback(func)``), then the first callback with a
matching ``func`` is removed, regardless of whether it was added with
or without ``*args, **kwargs``.

In a future version, ``Timer.remove_callback`` will always use the latter
behavior (not consider ``*args, **kwargs``); to specifically consider them, add
the callback as a `functools.partial` object ::

   cb = timer.add_callback(functools.partial(func, *args, **kwargs))
   # ...
   # later
   timer.remove_callback(cb)

`.backend_bases.Timer.add_callback` was modified to return *func* to
simplify the above usage (previously it returned None); this also
allows using it as a decorator.

The new API is modelled after `atexit.register` / `atexit.unregister`.

`~.collections.StemContainer` performance increase
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

`~.collections.StemContainer` objects can now store a
`~.collections.LineCollection` object instead of a list of
`~.lines.Line2D` objects for stem lines plotted using
`~.Axes.stem`. This gives a very large performance boost to displaying
and moving `~Axes.stem` plots.

This will become the default behaviour in Matplotlib 3.3. To use it
now, the *use_line_collection* keyword argument to `~.Axes.stem` can
be set to `True` ::

  ax.stem(..., use_line_collection=True)

Individual line segments can be extracted from the
`~.collections.LineCollection` using
`~.collections.LineCollection.get_segements()`. See the
`~.collections.LineCollection` documentation for other methods to
retrieve the collection properties.


`~matplotlib.colorbar.ColorbarBase` inheritance
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

`matplotlib.colorbar.ColorbarBase` is no longer a subclass of
`.cm.ScalarMappable`.  This inheritance lead to a confusing situation
where the `.cm.ScalarMappable` passed to `matplotlib.colorbar.Colorbar`
(`~.Figure.colorbar`) had a ``set_norm`` method, as did the colorbar.
The colorbar is now purely a follower to the `ScalarMappable` norm and
colormap, and the old inherited methods
`~matplotlib.colorbar.ColorbarBase.set_norm`,
`~matplotlib.colorbar.ColorbarBase.set_cmap`,
`~matplotlib.colorbar.ColorbarBase.set_clim` are deprecated, as are
the getter versions of those calls.  To set the norm associated with a
colorbar do ``colorbar.mappable.set_norm()`` etc.


FreeType and libpng search paths
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The ``MPLBASEDIRLIST`` environment variables and ``basedirlist`` entry in
``setup.cfg`` have no effect anymore.  Instead, if building in situations where
FreeType or libpng are not in the compiler or linker's default path, set the
standard environment variables ``CFLAGS``/``LDFLAGS`` on Linux or OSX, or
``CL``/``LINK`` on Windows, to indicate the relevant paths.

See details in `Installing`.

Setting artist properties twice or more in the same call
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Setting the same artist property multiple time via aliases is deprecated.
Previously, code such as ::

  plt.plot([0, 1], c="red", color="blue")

would emit a warning indicating that ``c`` and ``color`` are aliases
of one another, and only keep the ``color`` kwarg.  This behavior has
been deprecated; in a future version, this will raise a TypeError,
similar to Python's behavior when a keyword argument is passed twice ::

  plt.plot([0, 1], c="red", c="blue")

This warning is raised by `~.cbook.normalize_kwargs`.

Path code types
~~~~~~~~~~~~~~~
Path code types like ``Path.MOVETO`` are now ``np.uint8`` instead of ``int``
``Path.STOP``, ``Path.MOVETO``, ``Path.LINETO``, ``Path.CURVE3``,
``Path.CURVE4`` and ``Path.CLOSEPOLY`` are now of the type ``Path.code_type``
(``np.uint8`` by default) instead of plain ``int``. This makes their type
match the array value type of the ``Path.codes`` array.

LaTeX code in matplotlibrc file
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Previously, the rc file keys ``pgf.preamble`` and ``text.latex.preamble`` were
parsed using commmas as separators. This would break valid LaTeX code, such as::

  \usepackage[protrusion=true, expansion=false]{microtype}

The parsing has been modified to pass the complete line to the LaTeX system,
keeping all commas. Passing a list of strings from within a Python script still
works as it used to. Passing a list containing non-strings now fails, instead
of coercing the results to strings.

`.Axes.spy`
~~~~~~~~~~~

The method `.Axes.spy` now raises a `TypeError` for the keyword
arguments *interpolation* and *linestyle* instead of silently ignoring
them.

Furthermore, `.Axes.spy` spy does now allow for an *extent* argument
(was silently ignored so far).

A bug with `.Axes.spy(..., origin='lower')` is fixed.  Previously this
flipped the data but not the y-axis resulting in a mismatch between
axes labels and actual data indices. Now, *origin='lower'* flips both
the data and the y-axis labels.

Boxplot tick methods
~~~~~~~~~~~~~~~~~~~~

The *manage_xticks* parameter of `~.Axes.boxplot` and `~.Axes.bxp` has
been renamed (with a deprecation period) to *manage_ticks*, to take
into account the fact that it manages either x or y ticks depending on
the *vert* parameter.

When ``manage_ticks=True`` (the default), these methods now attempt to
take previously drawn boxplots into account when setting the axis
limits, ticks, and tick labels.

MouseEvents
~~~~~~~~~~~
MouseEvents now include the event name in their `str()`.
Previously they contained the prefix "MPL MouseEvent".

RGBA buffer return type
~~~~~~~~~~~~~~~~~~~~~~~

`.FigureCanvasAgg.buffer_rgba` and `.RendererAgg.buffer_rgba` now
return a memoryview The ``buffer_rgba`` method now allows direct
access to the renderer's underlying buffer (as a ``(m, n, 4)``-shape
memoryview) rather than copying the data to a new bytestring.  This is
consistent with the behavior on Py2, where a buffer object was
returned.


`matplotlib.font_manager.win32InstalledFonts` return type
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
`matplotlib.font_manager.win32InstalledFonts` returns an empty list instead
of None if no fonts are found.

`.Axes.fmt_xdata` and `.Axes.fmt_ydata` error handling
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Previously, if the user provided a `.Axes.fmt_xdata` or
`.Axes.fmt_ydata` function that raised a `TypeError` (or set them to a
non-callable), the exception would be silently ignored and the default
formatter be used instead.  This is no longer the case; the exception
is now propagated out.

Deprecation of redundant `Tick` attributes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The ``gridOn``, ``tick1On``, ``tick2On``, ``label1On``, and ``label2On``
`~.Tick` attributes have been deprecated.  Directly get and set the visibility
on the underlying artists, available as the ``gridline``, ``tick1line``,
``tick2line``, ``label1``, and ``label2`` attributes.

The ``label`` attribute, which was an alias for ``label1``, has been
deprecated.

Subclasses that relied on setting the above visibility attributes needs to be
updated; see e.g. :file:`examples/api/skewt.py`.

Passing a Line2D's drawstyle together with the linestyle is deprecated
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Instead of ``plt.plot(..., linestyle="steps--")``, use ``plt.plot(...,
linestyle="--", drawstyle="steps")``. ``ds`` is now an alias for ``drawstyle``.


``pgi`` support dropped
-----------------------

Support for ``pgi`` in the GTK3 backends has been dropped.  ``pgi`` is
an alternative implementation to ``PyGObject``.  ``PyGObject`` should
be used instead.

rcParam changes
---------------

Removed
~~~~~~~
The following deprecated rcParams have been removed:

- ``text.dvipnghack``
- ``nbagg.transparent`` (use :rc:`figure.facecolor` instead)
- ``plugins.directory``
- ``axes.hold``
- ``backend.qt4`` and ``backend.qt5`` (set the :envvar:`QT_API` environment
  variable instead)

Deprecated
~~~~~~~~~~
The associated validator functions ``rcsetup.validate_qt4`` and
``validate_qt5`` are deprecated.

The ``verbose.fileo`` and ``verbose.level`` rcParams have been deprecated.
These have had no effect since the switch from Matplotlib's old custom Verbose
logging to the stdlib's `logging` module. In addition the
``rcsetup.validate_verbose`` function is deprecated.

The ``text.latex.unicode`` rcParam now defaults to ``True`` and is
deprecated (i.e., in future versions
of Matplotlib, unicode input will always be supported).
Moreover, the underlying implementation now uses ``\usepackage[utf8]{inputenc}``
instead of ``\usepackage{ucs}\usepackage[utf8x]{inputenc}``.

Exception changes
-----------------
- `mpl_toolkits.axes_grid1.axes_size.GetExtentHelper` now raises `ValueError`
  for invalid directions instead of `KeyError`.
- Previously, subprocess failures in the animation framework would raise either
  in a `RuntimeError` or a `ValueError` depending on when the error occurred.
  They now raise a `subprocess.CalledProcessError` with attributes set as
  documented by the exception class.
- In certain cases, Axes methods (and pyplot functions) used to raise
  a `RuntimeError` if they were called with a ``data`` kwarg and
  otherwise mismatched arguments.  They now raise a `TypeError`
  instead.
- `.Axes.streamplot` does not support irregularly gridded ``x`` and ``y`` values.
  So far, it used to silently plot an incorrect result.  This has been changed to
  raise a `ValueError` instead.
- The `.streamplot.Grid` class, which is internally used by streamplot
  code, also throws a `ValueError` when irregularly gridded values are
  passed in.

Removals
--------
The following deprecated APIs have been removed:

Classes and methods
~~~~~~~~~~~~~~~~~~~
- ``Verbose`` (replaced by python logging library)
- ``artist.Artist.hitlist`` (no replacement)
- ``artist.Artist.is_figure_set`` (use ``artist.figure is not None`` instead)
- ``axis.Axis.unit_data`` (use ``axis.Axis.units`` instead)
- ``backend_bases.FigureCanvasBase.onRemove`` (no replacement)
  ``backend_bases.FigureManagerBase.show_popup`` (this never did anything)
- ``backend_wx.SubplotToolWx`` (no replacement)
- ``backend_wx.Toolbar`` (use ``backend_wx.NavigationToolbar2Wx`` instead)
- ``cbook.align_iterators`` (no replacment)
- ``contour.ContourLabeler.get_real_label_width`` (no replacement)
- ``legend.Legend.draggable`` (use `legend.Legend.set_draggable()` instead)
- ``texmanager.TexManager.postscriptd``, ``texmanager.TexManager.pscnt``,
  ``texmanager.TexManager.make_ps``, ``texmanager.TexManager.get_ps_bbox``
  (no replacements)

Arguments
~~~~~~~~~
- The *fig* kwarg to `.GridSpec.get_subplot_params` and
  `.GridSpecFromSubplotSpec.get_subplot_params` (use the argument
  *figure* instead)
- Passing 'box-forced' to `.Axes.set_adjustable` (use 'box' instead)
- Support for the strings 'on'/'true'/'off'/'false' to mean
  `True` / `False` (directly use `True` / `False` instead).
  The following functions are affected:

  - `.axes.Axes.grid`
  - `.Axes3D.grid`
  - `.Axis.set_tick_params`
  - `.pyplot.box`
- Using `.pyplot.axes` with an `.axes.Axes` type argument
  (use `.pyplot.sca` instead)

Other
~~~~~
The following miscellaneous API elements have been removed

- svgfont support (in :rc:`svg.fonttype`)
- Logging is now done with the standard python ``logging`` library.
  ``matplotlib.verbose`` and the command line switches ``--verbose-LEVEL`` have
  been removed.

  To control the logging output use::

    import logging
    logger = logging.getLogger('matplotlib')
    logger.set_level(logging.INFO)

- ``__version__numpy__``
- ``collections.CIRCLE_AREA_FACTOR``
- ``font_manager.USE_FONTCONFIG``
- ``font_manager.cachedir``

:mod:`matplotlib.mlab` removals
-------------------------------
Lots of code inside the :mod:`matplotlib.mlab` module which was deprecated
in Matplotlib 2.2 has been removed. See below for a list:

- ``mlab.exp_safe`` (use `numpy.exp` instead)
- ``mlab.amap``
- ``mlab.logspace`` (use `numpy.logspace` instead)
- ``mlab.rms_flat``
- ``mlab.l1norm`` (use ``numpy.linalg.norm(a, ord=1)`` instead)
- ``mlab.l2norm`` (use ``numpy.linalg.norm(a, ord=2)`` instead)
- ``mlab.norm_flat`` (use ``numpy.linalg.norm(a.flat, ord=2)`` instead)
- ``mlab.frange`` (use `numpy.arange` instead)
- ``mlab.identity`` (use `numpy.identity` instead)
- ``mlab.base_repr``
- ``mlab.binary_repr``
- ``mlab.ispower2``
- ``mlab.log2`` (use `numpy.log2` instead)
- ``mlab.isvector``
- ``mlab.movavg``
- ``mlab.safe_isinf`` (use `numpy.isinf` instead)
- ``mlab.safe_isnan`` (use `numpy.isnan` instead)
- ``mlab.cohere_pairs`` (use `scipy.signal.coherence` instead)
- ``mlab.entropy`` (use `scipy.stats.entropy` instead)
- ``mlab.normpdf`` (use `scipy.stats.norm.pdf` instead)
- ``mlab.find`` (use ``np.nonzero(np.ravel(condition))`` instead)
- ``mlab.longest_contiguous_ones``
- ``mlab.longest_ones``
- ``mlab.PCA``
- ``mlab.prctile`` (use `numpy.percentile` instead)
- ``mlab.prctile_rank``
- ``mlab.center_matrix``
- ``mlab.rk4`` (use `scipy.integrate.ode` instead)
- ``mlab.bivariate_normal``
- ``mlab.get_xyz_where``
- ``mlab.get_sparse_matrix``
- ``mlab.dist`` (use `numpy.hypot` instead)
- ``mlab.dist_point_to_segment``
- ``mlab.griddata`` (use `scipy.interpolate.griddata`)
- ``mlab.less_simple_linear_interpolation`` (use `numpy.interp`)
- ``mlab.slopes``
- ``mlab.stineman_interp``
- ``mlab.segments_intersect``
- ``mlab.fftsurr``
- ``mlab.offset_line``
- ``mlab.quad2cubic``
- ``mlab.vector_lengths``
- ``mlab.distances_along_curve``
- ``mlab.path_length``
- ``mlab.cross_from_above``
- ``mlab.cross_from_below``
- ``mlab.contiguous_regions`` (use `.cbook.contiguous_regions` instead)
- ``mlab.is_closed_polygon``
- ``mlab.poly_between``
- ``mlab.poly_below``
- ``mlab.inside_poly``
- ``mlab.csv2rec``
- ``mlab.rec2csv`` (use `numpy.recarray.tofile` instead)
- ``mlab.rec2text`` (use `numpy.recarray.tofile` instead)
- ``mlab.rec_summarize``
- ``mlab.rec_join``
- ``mlab.recs_join``
- ``mlab.rec_groupby``
- ``mlab.rec_keep_fields``
- ``mlab.rec_drop_fields``
- ``mlab.rec_append_fields``
- ``mlab.csvformat_factory``
- ``mlab.get_formatd``
- ``mlab.FormatDatetime`` (use `datetime.datetime.strftime` instead)
- ``mlab.FormatDate`` (use `datetime.date.strftime` instead)
- ``mlab.FormatMillions``, ``mlab.FormatThousands``, ``mlab.FormatPercent``,
  ``mlab.FormatBool``, ``mlab.FormatInt``, ``mlab.FormatFloat``,
  ``mlab.FormatFormatStr``, ``mlab.FormatString``, ``mlab.FormatObj``
- ``mlab.donothing_callback``

:mod:`matplotlib.pylab` removals
--------------------------------
Lots of code inside the :mod:`matplotlib.mlab` module which was deprecated
in Matplotlib 2.2 has been removed. This means the following functions are
no longer available in the `matplotlib.pylab` module:

- ``amap``
- ``base_repr``
- ``binary_repr``
- ``bivariate_normal``
- ``center_matrix``
- ``csv2rec`` (use `numpy.recarray.tofile` instead)
- ``dist`` (use `numpy.hypot` instead)
- ``dist_point_to_segment``
- ``distances_along_curve``
- ``entropy`` (use `scipy.stats.entropy` instead)
- ``exp_safe`` (use `numpy.exp` instead)
- ``fftsurr``
- ``find`` (use ``np.nonzero(np.ravel(condition))`` instead)
- ``frange`` (use `numpy.arange` instead)
- ``get_sparse_matrix``
- ``get_xyz_where``
- ``griddata`` (use `scipy.interpolate.griddata` instead)
- ``identity`` (use `numpy.identity` instead)
- ``inside_poly``
- ``is_closed_polygon``
- ``ispower2``
- ``isvector``
- ``l1norm`` (use ``numpy.linalg.norm(a, ord=1)`` instead)
- ``l2norm`` (use ``numpy.linalg.norm(a, ord=2)`` instead)
- ``log2`` (use `numpy.log2` instead)
- ``longest_contiguous_ones``
- ``longest_ones``
- ``movavg``
- ``norm_flat`` (use ``numpy.linalg.norm(a.flat, ord=2)`` instead)
- ``normpdf`` (use `scipy.stats.norm.pdf` instead)
- ``path_length``
- ``poly_below``
- ``poly_between``
- ``prctile`` (use `numpy.percentile` instead)
- ``prctile_rank``
- ``rec2csv`` (use `numpy.recarray.tofile` instead)
- ``rec_append_fields``
- ``rec_drop_fields``
- ``rec_join``
- ``rk4`` (use `scipy.integrate.ode` instead)
- ``rms_flat``
- ``segments_intersect``
- ``slopes``
- ``stineman_interp``
- ``vector_lengths``

mplot3d changes
---------------

Voxel shading
~~~~~~~~~~~~~
`.Axes3D.voxels` now shades the resulting voxels; for more details see
What's new. The previous behavior can be achieved by passing ::

  ax.voxels(.., shade=False)



Equal aspect axes disabled
~~~~~~~~~~~~~~~~~~~~~~~~~~

Setting the aspect on 3D axes previously returned non-sensical results
(e.g. see :ghissue:`1077`).  Calling ``ax.set_aspect('equal')`` or
``ax.set_aspect(num)`` on a 3D axes now raises a
`NotImplementedError`.

`.Poly3DCollection.set_zsort`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

`.Poly3DCollection.set_zsort` no longer silently ignores invalid
inputs, or `False` (which was always broken).  Passing `True` to mean
``"average"`` is deprecated.

Testing
-------
The ``--no-network`` flag to ``tests.py`` has been removed (no test requires
internet access anymore).  If it is desired to disable internet access both for
old and new versions of Matplotlib, use ``tests.py -m 'not network'`` (which is
now a no-op).

The image comparison test decorators now skip (rather than xfail) the test for
uncomparable formats. The affected decorators are `~.image_comparison` and
`~.check_figures_equal`. The deprecated `~.ImageComparisonTest` class is
likewise changed.

Dependency changes
------------------

NumPy
~~~~~
Matplotlib 3.1 now requires NumPy>=1.11.

ghostscript
~~~~~~~~~~~
Support for ghostscript 8.60 (released in 2007) has been removed.  The oldest
supported version of ghostscript is now 9.0 (released in 2010).

Mathtext changes
----------------
- In constructs such as ``"$1~2$"``, mathtext now interprets the tilde as a
  space, consistently with TeX (this was previously a parse error).

Deprecations
~~~~~~~~~~~~
- The ``\stackrel`` mathtext command hsa been deprecated (it behaved differently
  from LaTeX's ``\stackrel``.  To stack two mathtext expressions, use
  ``\genfrac{left-delim}{right-delim}{fraction-bar-thickness}{}{top}{bottom}``.
- The `\mathcircled` mathtext command (which is not a real TeX command)
  is deprecated.  Directly use unicode characters (e.g.
  ``"\N{CIRCLED LATIN CAPITAL LETTER A}"`` or ``"\u24b6"``) instead.
- Support for setting :rc:`mathtext.default` to circled is deprecated.

Signature deprecations
----------------------
The following signature related behaviours are deprecated:

- The *withdash* keyword argument to `.Axes.text()`. Consider using
  `.Axes.annotate()` instead.
- Passing (n, 1)-shaped error arrays to `.Axes.errorbar()`, which was not
  documented and did not work for ``n = 2``. Pass a 1D array instead.
- The *frameon* kwarg to `~.Figure.savefig` and the :rc:`savefig.frameon` rcParam.
  To emulate ``frameon = False``, set *facecolor* to fully
  transparent (``"none"``, or ``(0, 0, 0, 0)``).
- Passing a non-1D (typically, (n, 1)-shaped) input to `.Axes.pie`.
  Pass a 1D array instead.
- The `.TextPath` constructor used to silently drop ignored arguments; this
  behavior is deprecated.
- The *usetex* parameter of `.TextToPath.get_text_path` is deprecated and
  folded into the *ismath* parameter, which can now take the values
  `False`, `True`, and ``"TeX"``, consistently with other low-level
  text processing functions.
- Passing ``'normal'`` to `.axes.Axes.axis()` is deprecated, use
  ``ax.axis('auto')`` instead.
- Passing the *block* argument of `.pyplot.show` positionally is deprecated; it
  should be passed by keyword.
- When using the nbagg backend, `.pyplot.show` used to silently accept and ignore
  all combinations of positional and keyword arguments.  This behavior is
  deprecated.
- The unused *shape* and *imlim* parameters to `.Axes.imshow` are
  deprecated.  To avoid triggering the deprecation warning, the *filternorm*,
  *filterrad*, *resample*, and *url* arguments should be passed by
  keyword.
- The *interp_at_native* parameter to `.BboxImage`, which has had no effect
  since Matplotlib 2.0, is deprecated.
- All arguments to the `.cbook.deprecated` decorator and `.cbook.warn_deprecated`
  function, except the first one (the version where the deprecation occurred),
  are now keyword-only.  The goal is to avoid accidentally setting the "message"
  argument when the "name" (or "alternative") argument was intended, as this has
  repeatedly occurred in the past.
- The arguments of `matplotlib.testing.compare.calculate_rms` have been renamed
  from ``expectedImage, actualImage``, to ``expected_image, actual_image``.
- Passing positional arguments to `.Axis.set_ticklabels` beyond *ticklabels*
  itself has no effect, and support for them is deprecated.
- Passing ``shade=None`` to `~.axes3d.Axes3D.plot_surface` is deprecated. This
  was an unintended implementation detail with the same semantics as
  ``shade=False``. Please use the latter code instead.
- `matplotlib.ticker.MaxNLocator` and its *set_params* method will issue
  a warning on unknown keyword arguments instead of silently ignoring them.
  Future versions will raise an error.

Changes in parameter names
--------------------------

- The *arg* parameter to `matplotlib.use` has been renamed to *backend*.

  This will only affect cases where that parameter has been set
  as a keyword argument. The common usage pattern as a positional argument
  ``matplotlib.use('Qt5Agg')`` is not affected.
- The *normed* parameter to `Axes.hist2d` has been renamed to *density*.
- The *s* parameter to `Annotation` (and indirectly `Axes.annotation`) has
  been renamed to *text*.
- The *tolerence* parameter to
  `bezier.find_bezier_t_intersecting_with_closedpath`,
  `bezier.split_bezier_intersecting_with_closedpath`,
  `bezier.find_r_to_boundary_of_closedpath`,
  `bezier.split_path_inout` and `bezier.check_if_parallel` has been renamed to
  *tolerance*.

In each case, the old parameter name remains supported (it cannot be used
simultaneously with the new name), but support for it will be dropped in
Matplotlib 3.3.

Class/method/attribute deprecations
-----------------------------------



Support for custom backends that do not provide a
`.GraphicsContextBase.set_hatch_color` method is deprecated.  We
suggest that custom backends let their ``GraphicsContext`` class
inherit from `.GraphicsContextBase`, to at least provide stubs for all
required methods.

- `.spine.Spine.is_frame_like`

This has not been used in the codebase since its addition in 2009.

- `.axis3d.Axis.get_tick_positions`

  This has never been used internally, there is no equivalent method exists on
  the 2D Axis classes, and despite the similar name, it has a completely
  different behavior from the 2D Axis' `axis.Axis.get_ticks_position` method.
- `.backend_pgf.LatexManagerFactory`

- `.mpl_toolkits.axisartist.axislines.SimpleChainedObjects`
- `.mpl_toolkits.Axes.AxisDict`

Internal Helper Functions
~~~~~~~~~~~~~~~~~~~~~~~~~

- `.checkdep_dvipng`
- `.checkdep_ghostscript`
- `.checkdep_pdftops`
- `.checkdep_inkscape`


- `.ticker.decade_up`
- `.ticker.decade_down`


- `.cbook.dedent`
- `.docstring.Appender`
- `.docstring.dedent`
- `.docstring.copy_dedent`

Use the standard library's docstring manipulation tools instead, such as
`inspect.cleandoc` and `inspect.getdoc`.



- `matplotlib.scale.get_scale_docs()`
- `matplotlib.pyplot.get_scale_docs()`

These are considered internal and will be removed from the public API in a
future version.

- `.projections.process_projection_requirements`

- ``backend_ps.PsBackendHelper``
- ``backend_ps.ps_backend_helper``,

- `.cbook.iterable`
- `.cbook.get_label`
- `.cbook.safezip`
  Manually check the lengths of the inputs instead, or rely on NumPy to do it.
- `.cbook.is_hashable`
  Use ``isinstance(..., collections.abc.Hashable)`` instead.

- The `.backend_bases.RendererBase.strip_math`.  Use
  `.cbook.strip_math` instead.

Multiple internal functions that were exposed as part of the public API
of `.mpl_toolkits.mplot3d` are deprecated,

**mpl_toolkits.mplot3d.art3d**

- :func:`mpl_toolkits.mplot3d.art3d.norm_angle`
- :func:`mpl_toolkits.mplot3d.art3d.norm_text_angle`
- :func:`mpl_toolkits.mplot3d.art3d.path_to_3d_segment`
- :func:`mpl_toolkits.mplot3d.art3d.paths_to_3d_segments`
- :func:`mpl_toolkits.mplot3d.art3d.path_to_3d_segment_with_codes`
- :func:`mpl_toolkits.mplot3d.art3d.paths_to_3d_segments_with_codes`
- :func:`mpl_toolkits.mplot3d.art3d.get_patch_verts`
- :func:`mpl_toolkits.mplot3d.art3d.get_colors`
- :func:`mpl_toolkits.mplot3d.art3d.zalpha`

**mpl_toolkits.mplot3d.proj3d**

- :func:`mpl_toolkits.mplot3d.proj3d.line2d`
- :func:`mpl_toolkits.mplot3d.proj3d.line2d_dist`
- :func:`mpl_toolkits.mplot3d.proj3d.line2d_seg_dist`
- :func:`mpl_toolkits.mplot3d.proj3d.mod`
- :func:`mpl_toolkits.mplot3d.proj3d.proj_transform_vec`
- :func:`mpl_toolkits.mplot3d.proj3d.proj_transform_vec_clip`
- :func:`mpl_toolkits.mplot3d.proj3d.vec_pad_ones`
- :func:`mpl_toolkits.mplot3d.proj3d.proj_trans_clip_points`

If your project relies on these functions, consider vendoring them.


Font Handling
~~~~~~~~~~~~~

- `.backend_pdf.RendererPdf.afm_font_cache`
- `.backend_ps.RendererPS.afmfontd`
- `.font_manager.OSXInstalledFonts`
- `.TextToPath.glyph_to_path` (Instead call ``font.get_path()`` and manually transform the path.)


Date related functions
~~~~~~~~~~~~~~~~~~~~~~

- `.dates.seconds()`
- `.dates.minutes()`
- `.dates.hours()`
- `.dates.weeks()`
- `.dates.strpdate2num`
- `.dates.bytespdate2num`

These are brittle in the presence of locale changes.  Use standard datetime
parsers such as `time.strptime` or `dateutil.parser.parse`, and additionally
call `matplotlib.dates.date2num` if you need to convert to Matplotlib's
internal datetime representation; or use ``dates.datestr2num``.

Axes3D
~~~~~~

- `.axes3d.Axes3D.w_xaxis`
- `.axes3d.Axes3D.w_yaxis`
- `.axes3d.Axes3D.w_zaxis`

Use `.axes3d.Axes3D.xaxis`, `.axes3d.Axes3D.yaxis` and `.axes3d.Axes3D.zaxis`
instead.

Testing
~~~~~~~

- `matplotlib.testing.decorators.switch_backend` decorator

Test functions should use `pytest.mark.backend(...)`, and the mark will be
picked up by the `matplotlib.testing.conftest.mpl_test_settings` fixture.

Quiver
~~~~~~

- ``.color`` attribute of `Quiver` objects

Instead, use (as for any `Collection`) the ``get_facecolor`` method.
Note that setting to the ``.color`` attribute did not update the quiver artist,
whereas calling ``set_facecolor`` does.

GUI / backend details
~~~~~~~~~~~~~~~~~~~~~

- ``.get_py2exe_datafiles``
- ``.tk_window_focus``
- `.backend_gtk3.FileChooserDialog`
- `.backend_gtk3.NavigationToolbar2GTK3.get_filechooser`
- `.backend_gtk3.SaveFigureGTK3.get_filechooser`
- `.NavigationToolbar2QT.adj_window` attribute. This is unused and always ``None``.
- `.backend_wx.IDLE_DELAY` global variable
  This is unused and only relevant to the now removed wx "idling" code (note that
  as it is a module-level global, no deprecation warning is emitted when
  accessing it).
- `.mlab.demean`
- ``backend_gtk3cairo.FigureCanvasGTK3Cairo``,
- ``backend_wx.debug_on_error``, ``backend_wx.fake_stderr``,
  ``backend_wx.raise_msg_to_str``, ``backend_wx.MenuButtonWx``,
  ``backend_wx.PrintoutWx``,
- ``matplotlib.backends.qt_editor.formlayout`` module

This module is a vendored, modified version of the official formlayout_ module
available on PyPI. Install that module separately if you need it.

.. _formlayout: https://pypi.org/project/formlayout/

- `.GraphicsContextPS.shouldstroke`


Transforms / scales
~~~~~~~~~~~~~~~~~~~

- ``LogTransformBase``
- ``Log10Transform``
- ``Log2Transform``,
- ``NaturalLogTransformLog``
- ``InvertedLogTransformBase``
- ``InvertedLog10Transform``
- ``InvertedLog2Transform``
- ``InvertedNaturalLogTransform``

These classes defined in :mod:`matplotlib.scales` are deprecated.
As a replacement, use the general `LogTransform` and `InvertedLogTransform`
classes, whose constructors take a *base* argument.

Locators / Formatters
~~~~~~~~~~~~~~~~~~~~~

- ``OldScalarFormatter.pprint_val``
- ``ScalarFormatter.pprint_val``
- ``LogFormatter.pprint_val``

These are helper methods that do not have a consistent signature across
formatter classes.

Path tools
~~~~~~~~~~

- `.path.get_paths_extents`

Use `~.path.get_path_collection_extents` instead.

- `.Path.has_nonfinite` attribute

Use ``not np.isfinite(path.vertices).all()`` instead.

- `.bezier.find_r_to_boundary_of_closedpath` function is deprecated

This has always returned None instead of the requested radius.

Text
~~~~

- `.text.TextWithDash`
- `.Text.is_math_text`
- `.TextPath.is_math_text`
- `.TextPath.text_get_vertices_codes` (As an alternative, construct a new ``TextPath`` object.)

Unused attributes
~~~~~~~~~~~~~~~~~

- `.NavigationToolbar2QT.buttons`
- `.Line2D.verticalOffset`
- `.Quiver.keytext`
- `.Quiver.keyvec`
- `.SpanSelector.buttonDown`

These are unused and never updated.


Sphinx extensions
~~~~~~~~~~~~~~~~~

- ``matplotlib.sphinxext.mathmpl.math_directive``
- ``matplotlib.sphinxext.plot_directive.plot_directive``

This is because the ``matplotlib.sphinxext.mathmpl`` and
``matplotlib.sphinxext.plot_directive`` interfaces have changed from the
(Sphinx-)deprecated function-based interface to a class-based interface; this
should not affect end users.

- ``mpl_toolkits.axisartist.axis_artist.UnimplementedException``

Environmental Variables
~~~~~~~~~~~~~~~~~~~~~~~

- The ``MATPLOTLIBDATA`` environment variable


Axis
~~~~

- `.Axis.iter_ticks`

This only served as a helper to the private `.Axis._update_ticks`


Undeprecations
--------------
The following API elements have bee un-deprecated:

- The *obj_type* kwarg to the `.cbook.deprecated` decorator.
- *xmin*, *xmax* kwargs to `.Axes.set_xlim` and *ymin*, *ymax* kwargs
  to `.Axes.set_ylim`


New features
------------

`Text` now has a ``c`` alias for the ``color`` property
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For consistency with `.Line2D`, the `~.text.Text` class has gained the ``c``
alias for the ``color`` property. For example, one can now write ::

  ax.text(.5, .5, "foo", c="red")


``Cn`` colors now support ``n>=10``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It is now possible to go beyond the tenth color in the property cycle using
``Cn`` syntax, e.g. ::

  plt.plot([1, 2], color="C11")

now uses the 12th color in the cycle.

Note that previously, a construct such as::

  plt.plot([1, 2], "C11")

would be interpreted as a request to use color ``C1`` and marker ``1``
(an "inverted Y").  To obtain such a plot, one should now use ::

  plt.plot([1, 2], "1C1")

(so that the first "1" gets correctly interpreted as a marker
specification), or, more explicitly::

  plt.plot([1, 2], marker="1", color="C1")


New `.Formatter.format_ticks` method
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The `.Formatter` class gained a new `~.Formatter.format_ticks` method, which
takes the list of all tick locations as a single argument and returns the list
of all formatted values.  It is called by the axis tick handling code and, by
default, first calls `~.Formatter.set_locs` with all locations, then repeatedly
calls `~.Formatter.__call__` for each location.

Tick-handling code in the codebase that previously performed this sequence
(`~.Formatter.set_locs` followed by repeated `~.Formatter.__call__`) have been
updated to use `~.Formatter.format_ticks`.

`~.Formatter.format_ticks` is intended to be overridden by `.Formatter`
subclasses for which the formatting of a tick value depends on other tick
values, such as `.ConciseDateFormatter`.

Added support for RGB(A) images in pcolorfast
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

pcolorfast now accepts 3D images (RGB or RGBA) arrays if the X and Y
specifications allow image or pcolorimage rendering; they remain unsupported by
the more general quadmesh rendering


Invalid inputs
--------------

Passing invalid locations to `~.Axes.legend` and `~.Axes.table` used
to fallback on a default location.  This behavior is deprecated and
will throw an exception in a future version.

`.offsetbox.AnchoredText` is unable to handle the *horizontalalignment* or
*verticalalignment* kwargs, and used to ignore them with a warning.  This
behavior is deprecated and will throw an exception in a future version.

Passing steps less than 1 or greater than 10 to `~ticker..MaxNLocator` used to
result in undefined behavior.  It now throws a `ValueError`.

The signature of the (private) ``Axis._update_ticks`` has been changed to not
take the renderer as argument anymore (that argument is unused).
