How to add specific intervals of several lines?

Question

I have a file with several lines and I want to add a certain range considering all lines. To simplify, I took as an example:

AAA0000011111000090011
BBB0000011111000080011
CCC0000011111000070011

There are several more lines and fields too, but I know the interval I want to add. If you want to add up "00009", "00008" and "00007" which start in heading 14 and end in heading 18, what is the most efficient way? I also want to add "0011", "0011" and "0011". I want to write the fields in a new file.

The result would be a new file with the sums:

24
33

I thought as follows:

file_name = teste.GS3
arquivo = open(file_name, "r")
TOTAL_CHARGEABLE_UNITS = 0
DATA_VOLUME_OUTGOING = 0

i = True
for line in arquivo:
    if i: # para pular a primeira linha
        i = False
        continue
    TOTAL_CHARGEABLE_UNITS = TOTAL_CHARGEABLE_UNITS + sum(line[14:18] + ...)
    DATA_VOLUME_OUTGOING = DATA_VOLUME_OUTGOING + sum(line[19:22] + ...)
arquivo.close()

arquivo = open("/dados/cdrs-roaming/resultado.txt", "w")
arquivo.writelines([TOTAL_CHARGEABLE_UNITS],[DATA_VOLUME_OUTGOING])
arquivo.close

TOTAL_CHARGEABLE_UNITS and DATA_VOLUME_OUTGOING are the desired fields in this case. I am beginner so I had no idea how to create this sum. Any idea?

Detail: I believe I should convert these fields/ranges to float, but don’t know how to do this without converting the entire file.

Answer 1

As you are going through one line at a time, you will only have one value each iteration, so it makes no sense to use sum. Just update variables with each iteration:

total_chargeable_units = 0
data_volume_outgoing = 0
with open('arq.txt') as arq:
    # se quiser pular a primeira linha
    next(arq)

    for linha in arq:
        total_chargeable_units += int(linha[13:18])
        data_volume_outgoing += int(linha[18:22])

If you want to skip the first line, just call next on file before the for (and do not use the return for anything, so the first line will be ignored).

I converted the values to int because they are integers (I saw no need to use float). And within the loop i update the sums. Note that in Slice i put 13:18 (because the first position is zero, then the fourteenth character will be at position 13, and the last position - in this case, 18 - is not included).

Then just write to the results file:

with open('resultado.txt', 'w') as out:
    out.write(f'{total_chargeable_units}\n{data_volume_outgoing}')

Both to read and to write the files I used with, that ensures that the file is closed at the end (so you don’t need to call close).

---

If you want, you can also generalize, creating a dictionary with the names of the variables and their respective positions:

# guarda as posições inicial e final de cada variável
posicoes = {
    'total_chargeable_units': (13, 18),
    'data_volume_outgoing': (18, 22)
}

results = {}
with open('arq.txt') as arq:
    # se quiser pular a primeira linha
    next(arq)

    for linha in arq:
        # lê todas as posições e atualiza o valor das variáveis
        for variavel, (inicio, fim) in posicoes.items():
            try:
                results[variavel] = results.get(variavel, 0) + int(linha[inicio:fim])
            except ValueError:
                # se não tiver um número, mostra mensagem de erro
                print(f'Valor nas posições [{inicio}:{fim}] não é um número')

# grava tudo no arquivo
with open('resultado.txt', 'w') as out:
    for qtd in results.values():
        out.write(f'{qtd}\n')

I also included a validation if the file does not have a number in those positions.

The result will be another dictionary, containing the names of the variables and their respective totals.

Answer 2

Based on my colleague’s reply hkotsubo:

It helped a lot! I have not changed according to your second suggestion, but from your idea came up:

sequencia = ""
imsi = ""
msisdn = ""
operadora = ""
total_chargeable_units = 0
data_volume_outgoing = 0
gprs_apn_point = ""
with open('teste.GS3') as arq:
    # se quiser pular a primeira linha
    next(arq)

    for linha in arq:
        if imsi == linha[3:18]:
            msisdn = linha[188:209]
            operadora = linha[25:30]
            total_chargeable_units += int(linha[147:159])
            data_volume_outgoing += int(linha[159:171])
            gprs_apn_point = linha[237:300]
        else:
            sequencia = sequencia + imsi + ' ' + msisdn + ' ' + operadora + ' ' + str(total_chargeable_units) + ' ' + str(data_volume_outgoing) + ' ' + gprs_apn_point + '\n'
            imsi = linha[3:18]
            msisdn = linha[188:209]
            operadora = linha[25:30]
            total_chargeable_units = 0
            data_volume_outgoing = 0
            gprs_apn_point = linha[237:300]
            

    sequencia = sequencia + imsi + ' ' + msisdn + ' ' + operadora + ' ' + str(total_chargeable_units) + ' ' + str(data_volume_outgoing) + ' ' + gprs_apn_point + '\n'
            
with open('resultado.txt', 'w') as out:
    out.write(sequencia)