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from netCDF4 import Dataset, stringtochar, chartostring
import random, numpy, string
import unittest
import os
from numpy.testing import assert_array_equal, assert_array_almost_equal
def generateString(length, alphabet=string.ascii_letters + string.digits + string.punctuation):
return(''.join([random.choice(alphabet) for i in range(length)]))
# test conversion of arrays of fixed-length strings
# to arrays of characters (with an extra dimension), and vice-versa.
FILE_NAME = 'tst_stringarr.nc'
FILE_FORMAT = 'NETCDF4_CLASSIC'
n2 = 20; nchar = 12; nrecs = 4
data = numpy.empty((nrecs,n2),'S'+repr(nchar))
for nrec in range(nrecs):
for n in range(n2):
data[nrec,n] = generateString(nchar)
datau = data.astype('U')
datac = stringtochar(data, encoding='ascii')
class StringArrayTestCase(unittest.TestCase):
def setUp(self):
self.file = FILE_NAME
nc = Dataset(FILE_NAME,'w',format=FILE_FORMAT) # type: ignore # FILE_FORMAT
nc.createDimension('n1',None)
nc.createDimension('n2',n2)
nc.createDimension('nchar',nchar)
v = nc.createVariable('strings','S1',('n1','n2','nchar'))
v2 = nc.createVariable('strings2','S1',('n1','n2','nchar'))
# if _Encoding set, string array should automatically be converted
# to a char array and vice-versan
v2._Encoding = 'ascii'
v3 = nc.createVariable('strings3','S1',('n1','n2','nchar'))
v3._Encoding = 'ascii'
for nrec in range(nrecs):
datac = stringtochar(data,encoding='ascii')
v[nrec] = datac[nrec]
v2[:-1] = data[:-1]
v2[-1] = data[-1]
v2[-1,-1] = data[-1,-1] # write single element
v2[-1,-1] = data[-1,-1].tobytes() # write single python string
# _Encoding should be ignored if an array of characters is specified
v3[:] = stringtochar(data, encoding='ascii')
nc.close()
def tearDown(self):
# Remove the temporary files
os.remove(self.file)
def runTest(self):
"""testing functions for converting arrays of chars to fixed-len strings"""
nc = Dataset(FILE_NAME)
assert nc.dimensions['n1'].isunlimited() == True
v = nc.variables['strings']
v2 = nc.variables['strings2']
v3 = nc.variables['strings3']
assert v.dtype.str[1:] in ['S1','U1']
assert v.shape == (nrecs,n2,nchar)
for nrec in range(nrecs):
data2 = chartostring(v[nrec],encoding='ascii')
assert_array_equal(data2,datau[nrec])
data2 = v2[:]
data2[0] = v2[0]
data2[0,1] = v2[0,1]
assert_array_equal(data2,datau)
data3 = v3[:]
assert_array_equal(data3,datau)
# these slices should return a char array, not a string array
data4 = v2[:,:,0]
assert data4.dtype.itemsize == 1
assert_array_equal(data4, datac[:,:,0])
data5 = v2[0,0:nchar,0]
assert data5.dtype.itemsize == 1
assert_array_equal(data5, datac[0,0:nchar,0])
# test turning auto-conversion off.
v2.set_auto_chartostring(False)
data6 = v2[:]
assert data6.dtype.itemsize == 1
assert_array_equal(data6, datac)
nc.set_auto_chartostring(False)
data7 = v3[:]
assert data7.dtype.itemsize == 1
assert_array_equal(data7, datac)
nc.close()
if __name__ == '__main__':
unittest.main()
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