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def test():
"""
demonstrates basic pygrib functionality.
open a grib file, create an iterator.
>>> import pygrib
>>> list(pygrib.open('../sampledata/flux.grb'))
[1:Precipitation rate:kg m**-2 s**-1 (avg):regular_gg:surface:level 0:fcst time 108-120 hrs (avg):from 200402291200, 2:Surface pressure:Pa (instant):regular_gg:surface:level 0:fcst time 120 hrs:from 200402291200, 3:Maximum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200, 4:Minimum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200]
>>> pygrib.open('../sampledata/flux.grb').read()
[1:Precipitation rate:kg m**-2 s**-1 (avg):regular_gg:surface:level 0:fcst time 108-120 hrs (avg):from 200402291200, 2:Surface pressure:Pa (instant):regular_gg:surface:level 0:fcst time 120 hrs:from 200402291200, 3:Maximum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200, 4:Minimum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200]
>>> grbs = pygrib.open('../sampledata/flux.grb')
number of messages in file
>>> len(grbs)
4
acts like a file object
>>> grbs.tell()
0
>>> grbs.read(1)
[1:Precipitation rate:kg m**-2 s**-1 (avg):regular_gg:surface:level 0:fcst time 108-120 hrs (avg):from 200402291200]
>>> grbs.tell()
1
>>> grbs.read(2)
[2:Surface pressure:Pa (instant):regular_gg:surface:level 0:fcst time 120 hrs:from 200402291200, 3:Maximum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200]
>>> grbs.read()
[4:Minimum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200]
>>> grbs.seek(1)
>>> grbs.readline()
2:Surface pressure:Pa (instant):regular_gg:surface:level 0:fcst time 120 hrs:from 200402291200
>>> grbs.seek(-3,2)
>>> grbs.readline()
2:Surface pressure:Pa (instant):regular_gg:surface:level 0:fcst time 120 hrs:from 200402291200
>>> grbs.seek(1,1)
>>> grbs.readline()
4:Minimum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
>>> grbs.seek(0)
first grib message
>>> grb1 = grbs.readline()
>>> grb1
1:Precipitation rate:kg m**-2 s**-1 (avg):regular_gg:surface:level 0:fcst time 108-120 hrs (avg):from 200402291200
iterate over rest of grib messages.
>>> for grb in grbs: grb
2:Surface pressure:Pa (instant):regular_gg:surface:level 0:fcst time 120 hrs:from 200402291200
3:Maximum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
4:Minimum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
iterator now positioned at last message
>>> grb
4:Minimum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
grb1 is still first grib message
>>> grb1
1:Precipitation rate:kg m**-2 s**-1 (avg):regular_gg:surface:level 0:fcst time 108-120 hrs (avg):from 200402291200
position iterator at beginning again.
>>> grbs.rewind()
>>> for grb in grbs: grb
1:Precipitation rate:kg m**-2 s**-1 (avg):regular_gg:surface:level 0:fcst time 108-120 hrs (avg):from 200402291200
2:Surface pressure:Pa (instant):regular_gg:surface:level 0:fcst time 120 hrs:from 200402291200
3:Maximum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
4:Minimum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
get a specific grib message from the iterator.
iterator will be positioned at this message.
>>> grb = grbs.message(3)
>>> grb # 3rd message
3:Maximum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
indexing iterator with an integer key has the same result,
except that the position of iterator does not change.
>>> grbs.seek(0) # position iterator at beginning (same as grbs.rewind())
>>> grb = grbs[2] # 2nd message
>>> grb
2:Surface pressure:Pa (instant):regular_gg:surface:level 0:fcst time 120 hrs:from 200402291200
position iterator at next grib message.
>>> grb = grbs.readline()
>>> grb # back to the 1st message
1:Precipitation rate:kg m**-2 s**-1 (avg):regular_gg:surface:level 0:fcst time 108-120 hrs (avg):from 200402291200
use select method to choose grib messages based upon specified key/value pairs.
>>> selected_grbs = grbs.select(level=2,typeOfLevel='heightAboveGround') # get all 2-m level fields
>>> for grb in selected_grbs: grb
3:Maximum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
4:Minimum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
as above, but using step key (issue #9)
>>> selected_grbs = grbs.select(level=2,typeOfLevel='heightAboveGround',step=120)
>>> for grb in selected_grbs: grb
3:Maximum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
4:Minimum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
or create grib index instance for faster searching
>>> grbindx = pygrib.index('../sampledata/flux.grb','name','typeOfLevel','level')
>>> selgrbs = grbindx(name='Minimum temperature',level=2,typeOfLevel='heightAboveGround')
>>> for grb in selgrbs: grb
1:Minimum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
>>> selgrbs = grbindx(name='Maximum temperature',level=2,typeOfLevel='heightAboveGround')
>>> for grb in selgrbs: grb
1:Maximum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
>>> grbindx.write('flux.grb.idx') # save the index
>>> grbindx.close()
reload the saved index
>>> grbindx = pygrib.index('flux.grb.idx')
>>> selgrbs = grbindx(name='Minimum temperature',level=2,typeOfLevel='heightAboveGround')
>>> for grb in selgrbs: grb
1:Minimum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
>>> selgrbs = grbindx(name='Maximum temperature',level=2,typeOfLevel='heightAboveGround')
>>> for grb in selgrbs: grb
1:Maximum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
>>> grbindx.close()
>>> grb = selgrbs[0]
>>> grb
1:Maximum temperature:K (instant):regular_gg:heightAboveGround:level 2 m:fcst time 108-120 hrs:from 200402291200
get the data and the lat/lon values of the Max temp grid
>>> data = grb['values'] # 'values' returns the data
>>> 'shape/min/max data %s %6.2f %6.2f'%(str(data.shape),data.min(),data.max())
'shape/min/max data (94, 192) 223.70 319.90'
>>> lats, lons = grb.latlons() # returns lat/lon values on grid.
>>> str('min/max of %d lats on %s grid %4.2f %4.2f' % (grb['Nj'], grb['typeOfGrid'],lats.min(),lats.max()))
'min/max of 94 lats on regular_gg grid -88.54 88.54'
>>> str('min/max of %d lons on %s grid %4.2f %4.2f' % (grb['Ni'], grb['typeOfGrid'],lons.min(),lons.max()))
'min/max of 192 lons on regular_gg grid 0.00 358.12'
get 2nd grib message from the iterator
>>> grb = grbs.message(2)
>>> grb
2:Surface pressure:Pa (instant):regular_gg:surface:level 0:fcst time 120 hrs:from 200402291200
>>> 'valid date %s' % grb['validityDate']
'valid date 20040305'
>>> 'min/max %5.1f %5.1f' % (grb['minimum'],grb['maximum'])
'min/max 49650.0 109330.0'
change the forecast time.
gribmessage keys can be accessed either via attributes or key/value pairs.
>>> grb['forecastTime'] = 168
>>> grb['forecastTime']
168
>>> grb.forecastTime = 240
>>> grb.forecastTime
240
>>> grb['parameterNumber'] = 2 # change to pressure tendency
>>> data = grb['values']
>>> grb['values']=data/1000. # rescale
open an output file for writing
>>> grbout = open('test.grb','wb')
get coded binary string for modified message
>>> msg = grb.tostring()
write to file and close.
>>> ret = grbout.write(msg)
>>> grbout.close()
reopen file, check contents.
>>> grbs = pygrib.open('test.grb')
>>> grb = grbs.readline()
>>> grb
1:Pressure tendency:Pa s**-1 (instant):regular_gg:surface:level 0:fcst time 240 hrs:from 200402291200
>>> 'valid date %s' % grb['validityDate']
'valid date 20040310'
>>> grb.analDate
datetime.datetime(2004, 2, 29, 12, 0)
>>> grb.validDate
datetime.datetime(2004, 3, 10, 12, 0)
disable this test for now, since the result depends on the version
of grib_api installed.
#>>> str('min/max %4.2f %4.2f' % (grb['minimum'],grb['maximum']))
#'min/max 49.65 109.65'
>>> grbs.close()
test open.select with scalars, sequences and functions.
>>> grbs = pygrib.open('../sampledata/gfs.grb')
>>> sel_grbs = grbs.select(shortName='t',level=500)
>>> for grb in sel_grbs: grb
101:Temperature:K (instant):regular_ll:isobaricInhPa:level 50000 Pa:fcst time 72 hrs:from 201110080000
>>> sel_grbs = grbs.select(shortName='t',level=(850,700,500))
>>> for grb in sel_grbs: grb
101:Temperature:K (instant):regular_ll:isobaricInhPa:level 50000 Pa:fcst time 72 hrs:from 201110080000
133:Temperature:K (instant):regular_ll:isobaricInhPa:level 70000 Pa:fcst time 72 hrs:from 201110080000
157:Temperature:K (instant):regular_ll:isobaricInhPa:level 85000 Pa:fcst time 72 hrs:from 201110080000
>>> sel_grbs = grbs.select(shortName='t',level=lambda l: l < 500 and l >= 300)
>>> for grb in sel_grbs: grb
69:Temperature:K (instant):regular_ll:isobaricInhPa:level 30000 Pa:fcst time 72 hrs:from 201110080000
77:Temperature:K (instant):regular_ll:isobaricInhPa:level 35000 Pa:fcst time 72 hrs:from 201110080000
85:Temperature:K (instant):regular_ll:isobaricInhPa:level 40000 Pa:fcst time 72 hrs:from 201110080000
93:Temperature:K (instant):regular_ll:isobaricInhPa:level 45000 Pa:fcst time 72 hrs:from 201110080000
>>> from datetime import datetime
>>> sel_grbs = grbs.select(shortName='t',level=300,validDate=datetime(2011,10,11,0))
>>> for grb in sel_grbs: grb
69:Temperature:K (instant):regular_ll:isobaricInhPa:level 30000 Pa:fcst time 72 hrs:from 201110080000
>>> lats, lons = grb.latlons() # returns lat/lon values on grid.
>>> str('min/max of %d lats on %s grid %4.2f %4.2f' % (grb['Nj'], grb['typeOfGrid'],lats.min(),lats.max()))
'min/max of 73 lats on regular_ll grid -90.00 90.00'
test data subsetting via data method.
>>> datsubset,latsubset,lonsubset=grb.data(lat1=15,lat2=65,lon1=220,lon2=320)
>>> latsubset.min(),latsubset.max(),lonsubset.min(),lonsubset.max()
(15.0, 65.0, 220.0, 320.0)
>>> 'shape/min/max data subset %s %6.2f %6.2f' % (str(datsubset.shape),datsubset.min(),datsubset.max())
'shape/min/max data subset (21, 41) 219.70 247.60'
>>> grbstr = grb.tostring()
>>> grb2 = pygrib.fromstring(grbstr)
>>> grb2
1:Temperature:K (instant):regular_ll:isobaricInhPa:level 30000 Pa:fcst time 72 hrs:from 201110080000
>>> grb2.analDate
datetime.datetime(2011, 10, 8, 0, 0)
>>> grb2.validDate
datetime.datetime(2011, 10, 11, 0, 0)
>>> grbs.close()
>>> grbs = pygrib.open('../sampledata/gfs.t12z.pgrbf120.2p5deg.grib2')
>>> # see if multi-part grib messages are counted properly
>>> grbs.messages
343
>>> grbs.close()
test ndfd file with 'grid_complex_spatial_differencing' encoding
>>> grbs = pygrib.open('../sampledata/dspr.temp.bin')
>>> for grb in grbs: grb
1:Maximum temperature:K (max):mercator:surface:level 0:fcst time 2-14 hrs (max):from 201109292200
2:Maximum temperature:K (max):mercator:surface:level 0:fcst time 26-38 hrs (max):from 201109292200
3:Maximum temperature:K (max):mercator:surface:level 0:fcst time 50-62 hrs (max):from 201109292200
4:Maximum temperature:K (max):mercator:surface:level 0:fcst time 74-86 hrs (max):from 201109292200
>>> str(grb.packingType)
'grid_complex_spatial_differencing'
>>> data = grb.values
>>> grbs.close()
>>> str('min/max %5.2f %5.2f' % (data.min(), data.max()))
'min/max 295.40 308.10'
>>> grbs = pygrib.open('../sampledata/no-radius-shapeOfEarth-7.grb2')
>>> for grb in grbs: print(grb) # doctest:+ELLIPSIS
1:Total precipitation:kg m-2 (accum):lambert:surface:level 0:fcst time 15...-30... mins (accum):from 201804100000
>>> str(grb.packingType)
'grid_simple'
>>> grbs.close()
"""
if __name__ == "__main__":
import doctest
failure_count, test_count = doctest.testmod(verbose=True)
import pygrib, sys
sys.stdout.write('using ECCODES library version %s\n' % pygrib.grib_api_version)
if failure_count==0:
sys.exit(0)
else:
sys.exit(1)
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