GRIB-944: Add Python example showing how to query the bitmap array

examples/python/grib_iterator.py

@@ -4,9 +4,8 @@
 # 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.
+# 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

examples/python/grib_iterator.sh

@@ -4,12 +4,17 @@
 
 TEMP1=temp1.$$
 TEMP2=temp2.$$
+TEMP3=temp3.$$
 
+# Input file with some missing data values
 FILE="${data_dir}/reduced_latlon_surface.grib1"
 $PYTHON $examples_src/grib_iterator.py $FILE 2> $TEMP1 > $TEMP1
-./p_grib_iterator $FILE        2> $TEMP2 > $TEMP2
+./p_grib_iterator $FILE                      2> $TEMP2 > $TEMP2
 diff $TEMP1 $TEMP2
 
+$PYTHON $examples_src/grib_iterator_bitmap.py $FILE 2> $TEMP3 > $TEMP3
+diff $TEMP1 $TEMP3
+
 
 # Polar stereographic
 FILE="${ECCODES_SAMPLES_PATH}/polar_stereographic_pl_grib2.tmpl"
@@ -17,5 +22,8 @@ $PYTHON $examples_src/grib_iterator.py $FILE 2> $TEMP1 > $TEMP1
 ./p_grib_iterator $FILE        2> $TEMP2 > $TEMP2
 diff $TEMP1 $TEMP2
 
+$PYTHON $examples_src/grib_iterator_bitmap.py $FILE 2> $TEMP3 > $TEMP3
+diff $TEMP1 $TEMP3
 
-rm $TEMP1 $TEMP2 || true
+
+rm $TEMP1 $TEMP2 $TEMP3 || true

examples/python/grib_iterator_bitmap.py

@@ -0,0 +1,73 @@
+#
+# Copyright 2005-2016 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
+
+
+def example(INPUT):
+    f = open(INPUT)
+
+    while 1:
+        gid = codes_grib_new_from_file(f)
+        if gid is None:
+            break
+
+        iterid = codes_grib_iterator_new(gid, 0)
+
+        bitmapPresent = codes_get(gid, 'bitmapPresent')
+        if bitmapPresent:
+            # Get the bitmap array which contains 0s and 1s
+            bitmap = codes_get_array(gid, 'bitmap', int)
+            # Do some sanity checking
+            assert len(bitmap) == codes_get_size(gid, 'values')
+            assert len(bitmap) == codes_get(gid, 'numberOfDataPoints')
+
+        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))
+
+            # Consult bitmap to see if the i'th value is missing
+            if bitmapPresent and bitmap[i] == 0:
+                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, err:
+        if VERBOSE:
+            traceback.print_exc(file=sys.stderr)
+        else:
+            print >>sys.stderr, err.msg
+
+        return 1
+
+if __name__ == "__main__":
+    sys.exit(main())