Psyplot, and especially it's plugins have a lot of configuration values. Our rcParams handling is motivated by :ref:`matplotlib <matplotlib:matplotlibrc-sample>` although we extended the possibilities of it's :class:`matplotlib.RcParams` class. Our rcParams are stored in the :attr:`psyplot.rcParams <psyplot.config.rcsetup.rcParams>` object. Without any plugins, this looks like

.. ipython::

    @verbatim
    In [1]: from psyplot import rcParams

    @suppress
    In [1]: # is not shown because we have to disable the plugins
       ...: from psyplot.config.rcsetup import RcParams, defaultParams_orig
       ...:
       ...: rcParams = RcParams(defaultParams=defaultParams_orig)
       ...: rcParams.update_from_defaultParams()

    In [2]: print(rcParams.dump(exclude_keys=[]))

You can use this object like a dictionary and modify the default values. For example, if you do not want, that the seaborn package is imported when the :mod:`psyplot.project` module is imported, you can simply do this via:

.. ipython::

    In [3]: rcParams["project.import_seaborn"] = False

Additionally, you can make these changes permanent. At every first import of the psyplot module, the rcParams are updated from a yaml configuration file. On Linux and OS X, this is stored under $HOME/.config/psyplot/psyplotrc.yml, under Windows it is stored at $HOME/.psyplot/psyplotrc.yml. But use the :func:`psyplot.config.rcsetup.psyplot_fname` function, to get the correct location.

To make our changes from above permanent, we could just do:

.. ipython::

    In [4]: import yaml
       ...: from psyplot.config.rcsetup import psyplot_fname

    In [5]: with open(psyplot_fname(if_exists=False), "w") as f:
       ...:     yaml.dump({"project.import_seaborn": False}, f)

    # or we use the dump method
    In [6]: rcParams.dump(
       ...:     psyplot_fname(if_exists=False),
       ...:     overwrite=True,  # update the existing file
       ...:     include_keys=["project.import_seaborn"],
       ...: )

The psyplot plugins, (:mod:`psy_simple.plugin`, :mod:`psy_maps.plugin`, etc.) define their own :data:`~psy_simple.plugin.rcParams` instance. When the plugins are loaded at the first import of psyplot, these instances update :attr:`psyplot.rcParams <psyplot.config.rcsetup.rcParams>`.

The update mainly defines the default values for the plotters defined by that plugin. However, it is not always obvious, which key in the :attr:`psyplot.rcParams <psyplot.config.rcsetup.rcParams>` belongs to which formatoption. For this purpose, however, you can use the :attr:`~psyplot.plotter.Formatoption.default_key` attribute. For example, the :attr:`title <psy_simple.plotters.LinePlotter.title>` formatoption has the default_key

.. ipython::

    In [7]: import psyplot.project as psy

    In [8]: plotter = psy.plot.lineplot.plotter_cls()
       ...: plotter.title.default_key

As our plotters are based on inheritance, the default values use it, too. Therefore, the :class:`~psy_maps.plotters.FieldPlotter`, the underlying plotter for the :attr:`~psyplot.Project.ProjectPlotter.mapplot` plot method, uses the same configuration value in the :attr:`psyplot.rcParams <psyplot.config.rcsetup.rcParams>`:

.. ipython::

    In [9]: plotter = psy.plot.mapplot.plotter_cls()
       ...: plotter.title.default_key