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from os.path import isfile
from netCDF4 import Dataset as netCDF4_Dataset
from ..constants import _file_to_fh
from ..functions import open_files_threshold_exceeded, close_one_file
#if 'netCDF' not in _file_to_fh:
# _file_to_fh['netCDF'] = {}
_file_to_Dataset = _file_to_fh.setdefault('netCDF', {})
def _open_netcdf_file(filename, mode, fmt='NETCDF4'):
'''
Open a netCDF file and read it into a netCDF4.Dataset object.
If the file is already open then the existing netCDF4.Dataset object
will be returned.
:Parameters:
filename : str
The netCDF file to be opened.
:Returns:
out : netCDF4.Dataset
A netCDF4.Dataset instance for the netCDF file.
:Examples:
>>> nc1 = _open_netcdf_file('file.nc')
>>> nc1
<netCDF4.Dataset at 0x1a7dad0>
>>> nc2 = _open_netcdf_file('file.nc')
>>> nc2 is nc1
True
'''
if filename in _file_to_Dataset and mode == 'r':
# File is already open
return _file_to_Dataset[filename]
elif open_files_threshold_exceeded():
# Close a random data file to make way for this one
close_one_file()
if mode in ('a', 'r+'):
if not isfile(filename):
nc = netCDF4_Dataset(filename, 'w', format=fmt)
nc.close()
elif filename in _file_to_Dataset:
_close_netcdf_file(filename)
try:
nc = netCDF4_Dataset(filename, mode, format=fmt)
except RuntimeError as runtime_error:
raise RuntimeError("{0}: {1}".format(runtime_error, filename))
if mode == 'r':
# Update the _file_to_Dataset dictionary
_file_to_Dataset[filename] = nc
return nc
#--- End: def
def _close_netcdf_file(filename):
'''
Close a netCDF file
does nothing if the file is already closed.
:Parameters:
filename : str
The netCDF file to be closed.
:Returns:
None
:Examples:
'''
nc = _file_to_Dataset.pop(filename, None)
if nc is not None:
nc.close()
#--- End: def
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