"""
Readers
=======
Readers are responsible for providing Opendrift with data about the
`enviornment` of the drifting particles or elements.
All readers descend from :class:`.basereader.BaseReader`. A reader generally also descends from one of the few general classes of readers. When writing a new reader consider which one fits your input data best:
* :class:`.basereader.continuous.ContinuousReader`
* :class:`.basereader.structured.StructuredReader`
* :class:`.basereader.unstructured.UnstructuredReader`
The `ContinuousReader` is suited for data that can be defined at any point within the domain, or if the reader does its own interpolation internally. E.g. a :class:`synthetic eddy <.reader_ArtificialOceanEddy.Reader>`, or a :class:`constant <.reader_constant.Reader>`. The `StructuredReader` aids in interpolation when creating a reader of data on a :class:`regular grid <.reader_netCDF_CF_generic.Reader>`, while the `UnstructuredReader` provides the basics for :class:`irregularily gridded data <.reader_netCDF_CF_unstructured.Reader>` (e.g. finite volume models).
.. seealso::
See the reader-types or reader-implementations for more details.
See :class:`.basereader.BaseReader` for how readers work internally.
"""
import importlib
import logging; logger = logging.getLogger(__name__)
import glob
import json
import opendrift
[docs]def reader_from_url(url, timeout=10):
'''Make readers from URLs or paths to datasets'''
if isinstance(url, list):
return [reader_from_url(u) for u in url]
try: # Initialise reader from JSON string
j = json.loads(url)
try:
reader_module = importlib.import_module(
'opendrift.readers.' + j['reader'])
reader = getattr(reader_module, 'Reader')
del j['reader']
reader = reader(**j)
return reader
except Exception as e:
logger.warning('Creating reader from JSON failed:')
logger.warning(e)
except:
pass
if len(glob.glob(url)) == 0: # Check if this is a URL, and not giving timeout
import requests
try:
resp = requests.get(url, timeout=timeout)
except requests.exceptions.MissingSchema:
logger.info('Neither a file or a URL: ' + url)
return None
except:
logger.info('Connection error for ' + url)
return None
reader_modules = ['reader_netCDF_CF_generic',
'reader_ROMS_native',
'reader_grib']
for rm in reader_modules:
reader_module = importlib.import_module('opendrift.readers.' + rm)
try:
r = reader_module.Reader(url)
return r
except Exception as e:
print('Could not open %s with %s' % (url, rm))
return None # No readers worked