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Read the GTS bulletin keys as well as GRIB/BUFR messages

Step-by-step guide

You have an input file containing GRIB or BUFR messages but each one of the messages also has a GTS wrapper. You want to print the GTS keys as well as the GRIB/BUFR keys for all these messages.

Each block looks something like this (repeated for each message):

The example below shows a Python script which

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has two loops: The first one over the GTS messages and the second loop over the GRIB messages. In the first pass we store the GTS key values into a dictionary for later access (a dictionary whose key is the message number and whose value is another dictionary storing the GTS keys and their values)
When we come to the GRIB messages we access the dictionary to get the relevant GTS keys.

To read BUFR messages instead, simply change the call from "codes_grib_new_from_file

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" to "codes_bufr_new_from_file".

from eccodes import *

INPUT = sys.argv[1]
mydict = {}

# GTS loop
cnt = 0
with open(INPUT, 'rb') as fin:
    while 1:

...

...

...

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gts = codes_gts_new_from_file(fin)
        if gts is None:
            break

...

...

# 

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Get 

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the relevant keys from the GTS bulletin
  

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...

...

...

...

...

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cnt 

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+= 

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1
        tt = codes_get(gts, 'TT')
        aa = codes_get(gts, 'AA')
        ii = codes_get(gts, 'II')
        mydict[cnt] = 

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{'TT': tt, 'AA': aa, 'II': ii}
        

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codes_release(gts)

# BUFR/GRIB loop
cnt = 0
with open(INPUT, 'rb') as fin:
    while 1:
        msgid = codes_grib_new_from_file(fin

...

)
        if msgid is None:
            break
        

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cnt += 1
        sn = codes_get(msgid, '

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shortName')
        idict = mydict[cnt] # Access GTS values
        tt 

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= idict['TT']
        aa = idict['AA']
        ii = idict['II']
        print(tt, aa, ii, 

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sn)
        codes_release(msgid)

Each BUFR message is enclosed in the GTS header/footer so after reading the first GTS message, the file pointer has moved on after the enclosed BUFR so we need to rewind it before reading the next GTS message.

Note: Sometimes a GTS envelope may include multiple GRIB/BUFR messages. The example above assumes that for each GTS wrapper there is exactly one GRIB/BUFR message.

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