The application can catch the exception and re-request that chain RIC for specific times. The code looks like:

universe = pd.read_csv('chain.csv', delimiter=',', header=None)
universe = universe.values.T.tolist()[0]
for u in universe:
    i = 0    
    while (i < 3):
        try:
            data_grid, err = ek.get_data(u,['BKGD_REF'])
            print ("Success:", u)
            i = 3
        except:
            print ("Exception:", u)
            i = i + 1

It could be server timeout. Requesting one RIC at a time is not effective.

You need to request by using a list of instruments instead.

def chunks(chunkable, n):
    """ Yield successive n-sized chunks from l.
    """
    for i in range(0, len(chunkable), n):
        yield chunkable[i:i+n]
        
universe = pd.read_csv('rics.csv', delimiter=',', header=None)
universe = universe.values.T.tolist()[0]
for l in list(chunks(universe, 200)):
    data_grid, err = ek.get_data(l,['BKGD_REF'])
    print (data_grid)

Thank for your answer, usually I do batch processing (like your code above). Except that I did not specify that my file rics.csv contained rics options ie:

0#BFB*.U
0#AIV*.U
0#AJG*.U
0#BXP*.U
0#AES*.U
0#AVB*.U
0#APH*.U
0#AIZ*.U
0#CCI*.U
0#BDX*.U
0#AYI*.U
0#BWA*.U
0#ADSK*.U
etc..

So I have to do it 1 by 1. Does the 400 appear if a ric doesn't exist ?

data_grid, err = ek.get_data(['0#AVB*.U','0#APH*.U'],['BKGD_REF'])
print(data_grid)
data_grid, err = ek.get_data(['0#AVB*.U'],['BKGD_REF'])
print(data_grid)
data_grid, err = ek.get_data(['0#APH*.U'],['BKGD_REF'])
print(data_grid) 

I have tested it with an invalid RIC, such as BFBB161806000x.U and it also returns NaN.

One scenario which cause 400 Bad Request is server timeout. If the request takes more than a specific time slice to process on the server, the request will be timeout and the server will send a response with 400 code and "Backend error. 400 Bad Request" text.

HTTP/1.1 200 OK
...
Content-Length: 65
{"ErrorCode":400,"ErrorMessage":"Backend error. 400 Bad Request"}

Therefore, if this issue happens randomly and is not link to a specific request, it could be server time.

Could you please share the full rics.csv file? Therefore, we can test it and verify if it is server timeout.

Your code returns "NaN" because there is no BKGD_REF on options (BFBB161806000x.U)

But before questioning the option:

data_grid, err = ek.get_data(['BFBB161806000x.U'],['BKGD_REF'])

I need to retrieve the list of options available for each RIC.

Example for AVN :

data_grid, err = ek.get_data(['0#AVB*.U'],['BKGD_REF']) 
print(data_grid) 

Result :

===================== RESTART demo.py =====================
          Instrument         BKGD_REF
0                AVB             None
1    AVBB161813500.U  AVBB1618C135000
2    AVBN161813500.U  AVBN1618C135000
3    AVBB161814000.U  AVBB1618C140000
4    AVBN161814000.U  AVBN1618C140000
5    AVBB161814500.U  AVBB1618C145000
6    AVBN161814500.U  AVBN1618C145000
7    AVBB161815000.U  AVBB1618C150000
8    AVBN161815000.U  AVBN1618C150000
9    AVBB161815500.U  AVBB1618C155000
10   AVBN161815500.U  AVBN1618C155000
11   AVBB161816000.U  AVBB1618C160000

But you have to do it 1 by 1. Because if you do it by batch

data_grid, err = ek.get_data(['0#AVB*.U','0#APH*.U'],['BKGD_REF'])
print(data_grid)

Result :

Instrument  BKGD_REF
0   0#AVB*.U       NaN
1   0#APH*.U       NaN

Sorry, I can not provide the list of 600 rics however here are 25 rics that generates a 400:

0#AJG*.U
0#BXP*.U
0#AES*.U
0#TRMB*.U
0#UMPQ*.U
0#WAB*.U
0#ADSK*.U
0#APD*.U
0#ADP*.U
0#BBBY*.U
0#ALK*.U
0#AZO*.U
0#ADS*.U
0#AMAT*.U
0#AIG*.U
0#AMGN*.U
0#ABT*.U
0#ADM*.U
0#APA*.U
0#BSX*.U
0#CBS*.U
0#CBSH*.U
0#APC*.U
0#AXP*.U
0#AMG*.U

then with the following code, (I replaced BKGD_REF with CF_NAME)

# Rics (0#AMG*.U, 0#AXP*.U, etc..)
universe = pd.read_csv('rics.csv', delimiter=',', header=None)
universe = universe.values.T.tolist()[0]

# --------------------------
# Get Ric Option
# --------------------------
for u in universe:
    data_grid, err = ek.get_data(u,['CF_NAME'])
    print(data_grid)

The issue with error 400 is that it appears randomly and break the code

rics.txt. (please, change the extension to csv)