Description
This example shows: how to use an iterator on lat/lon/values for GRIB messages
Source code
grib_iterator.py
# # (C) Copyright 2005- ECMWF. # # This software is licensed under the terms of the Apache Licence Version 2.0 # which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. # # In applying this licence, ECMWF does not waive the privileges and immunities granted to it by # virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction. # import traceback import sys from eccodes import * VERBOSE = 1 # verbose error reporting missingValue = 1.0e36 # A value out of range def example(INPUT): f = open(INPUT, "rb") while 1: gid = codes_grib_new_from_file(f) if gid is None: break bitmapPresent = codes_get(gid, "bitmapPresent") if bitmapPresent: # Set the value representing the missing value in the field. # Choose a missingValue that does not correspond to any real value in the data array codes_set(gid, "missingValue", missingValue) iterid = codes_grib_iterator_new(gid, 0) i = 0 while 1: result = codes_grib_iterator_next(iterid) if not result: break [lat, lon, value] = result sys.stdout.write("- %d - lat=%.6e lon=%.6e value=" % (i, lat, lon)) if bitmapPresent and value == missingValue: print("missing") else: print("%.6f" % value) i += 1 codes_grib_iterator_delete(iterid) codes_release(gid) f.close() def main(): try: example(sys.argv[1]) except CodesInternalError as err: if VERBOSE: traceback.print_exc(file=sys.stderr) else: sys.stderr.write(err.msg + '\n') return 1 if __name__ == "__main__": sys.exit(main())
grib_iterator.c
/* * (C) Copyright 2005- ECMWF. * * This software is licensed under the terms of the Apache Licence Version 2.0 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. * * In applying this licence, ECMWF does not waive the privileges and immunities granted to it by * virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction. */ /* * C Implementation: grib_iterator * * Description: how to use an iterator on lat/lon/values for GRIB messages */ #include <stdio.h> #include <stdlib.h> #include "eccodes.h" static void usage(const char* prog) { printf("Usage: %s grib_file\n", prog); exit(1); } int main(int argc, char** argv) { FILE* in = NULL; int err = 0; double lat, lon, value; double missingValue = 1.0e36; /* A value out of range */ int n = 0; long bitmapPresent = 0; char* filename = NULL; /* Message handle. Required in all the ecCodes calls acting on a message.*/ codes_handle* h = NULL; /* Iterator on lat/lon/values.*/ codes_iterator* iter = NULL; if (argc != 2) usage(argv[0]); filename = argv[1]; in = fopen(filename, "rb"); if (!in) { fprintf(stderr, "Error: unable to open file %s\n", filename); return 1; } /* Loop on all the messages in a file.*/ while ((h = codes_handle_new_from_file(0, in, PRODUCT_GRIB, &err)) != NULL) { /* Check of errors after reading a message. */ if (err != CODES_SUCCESS) CODES_CHECK(err, 0); /* Check if a bitmap applies */ CODES_CHECK(codes_get_long(h, "bitmapPresent", &bitmapPresent), 0); if (bitmapPresent) { /* Set the double representing the missing value in the field. */ /* Choose a missingValue that does not correspond to any real value in the data array */ CODES_CHECK(codes_set_double(h, "missingValue", missingValue), 0); } /* A new iterator on lat/lon/values is created from the message handle h. */ iter = codes_grib_iterator_new(h, 0, &err); if (err != CODES_SUCCESS) CODES_CHECK(err, 0); n = 0; /* Loop on all the lat/lon/values. */ while (codes_grib_iterator_next(iter, &lat, &lon, &value)) { /* You can now print lat and lon, */ printf("- %d - lat=%f lon=%f value=", n, lat, lon); /* decide what to print if a missing value is found. */ if (bitmapPresent && value == missingValue) printf("missing\n"); /* and print the value if is not missing. */ else printf("%f\n", value); n++; } /* At the end the iterator is deleted to free memory. */ codes_grib_iterator_delete(iter); /* At the end the codes_handle is deleted to free memory. */ codes_handle_delete(h); } fclose(in); return 0; }
1 Comment
Shahram Najm
Also see grib_iterator_bitmap