The top level cartopy module contains the :attr:`~cartopy.config` dictionary which controls various aspects of cartopy's behaviour.
.. py:data:: cartopy.config
The config dictionary stores global configuration values for cartopy.
In the first instance, the config is defined in ``cartopy/__init__.py``. It
is possible to provide site wide customisations by including a
``siteconfig.py`` file along with the cartopy source code. ``siteconfig.py``
should contain a function called ``update_config`` which takes the config
dictionary instance as its first and only argument (from where it is
possible to update the dictionary howsoever desired).
For users without write permission to the cartopy source directory, a package
called ``cartopy_userconfig`` should be made importable (consider putting it
in ``site.getusersitepackages()``) and should expose a
function called ``update_config`` which takes the config dictionary as its
first and only argument.
Keys in the config dictionary:
``pre_existing_data_dir``
The absolute path to a directory where standard data (such as that from
NaturalEarth) can be found. If it is not found in this location the
``data_dir`` config item will be used.
``data_dir``
The absolute path to a directory where standard data (such as that from
NaturalEarth) can be found. If it is not found and the item is
downloadable cartopy will download the appropriate file(s) to a
subdirectory of this directory, therefore ``data_dir`` should be
writable by the user.
``repo_data_dir``
The absolute path to the directory where the data delivered with the
cartopy repository is stored. Typically this will only be set by OS
packagers and system administrators for site wide deployments.
``downloaders``
A dictionary mapping standard "specifications" to the appropriate
:class:`~cartopy.io.Downloader`. For further documentation and an
example see :func:`cartopy.io.Downloader.from_config`.