filename = 'OMI_BEHR_' + year + month + day + '.hdf'
filedir = ('C:/BEHR/' + year + '/' + month + '/')
os.chdir(filedir)
a = os.path.isfile(filename)
if a == False:
    print 'File ' + filename + 'is not available'
    continue
else:
    f = h5py.File(filedir + filename,'r')
    group = f['Data/']
    L = list(group)
    for h in range(0, len(L)):
        swath = L[h]
        swathval = int(swath[5:])
        group = f['Data/Swath' + str(swathval)]
        latitude = group['Latitude'].value