List Comprehension returning zero

Question

Guys, I need your help. I have a code in python that I would like to return the amount of values that meet a criterion, but it is returning zero. The txt file contains data like this:

567886786765211267878783647866575678666869837678681226786789 cancelado

562342342342343123124234534645656756756756756756756765756178 assinado

555456456546544324234235434534645645645645654645645645645631 assinado

520757345873458374657834857897989988786785645342111575756432 cancelado

554234534534645647567867987089078655345231342536456575676777 cancelado

That’s the return I’m getting:

{'P1': {'Total': 2, 'Ativos': 0}, 'P2': {'Total': 2, 'Ativos': 0}, 'P3': {'Total': 1, 'Ativos': 0}}

And I’d like him to return to me like this:

{'P1': {'Total': 2, 'Ativos': 0}, 'P2': {'Total': 2, 'Ativos': 1}, 'P3': {'Total': 1, 'Ativos': 1}}

That is the code

with open('log.txt','r') as file:
    arquivo = filter(None, [line.rstrip('\n').split() for line in file])

prefixo = []
    status = []
    for linha in arquivo:
        prefixo.append(linha[0][:2])
        status.append(linha[1])
    data = zip(prefixo, status)
    
paises = {
    'P1': {
        'Total': [p for p in prefixo if p == '55'].count('55'),
        'Ativos': [d for d in data if d[0] == '55' and d[1] == 'assinado'].count('assinado')
    },
    'P2': {
        'Total': [p for p in prefixo if p == '56'].count('56'),
        'Ativos': [d for d in data if d[0] == '56' and d[1] == 'assinado'].count('assinado')
    },

    'P3': {
        'Total': [p for p in prefixo if p == '52'].count('52'),
        'Ativos': [d for d in data if d[0] == '52' and d[1] == 'assinado'].count('assinado')
    },
}

If you can help me

Answer 1

The problem is that zip returns an iterable which can only be traversed/iterated once. Example:

x = [1, 2, 3]
y = [ 'a', 'b', 'c']
z = zip(x, y)

print('primeira vez:', [ d for d in z ])
print('segunda vez:', [ d for d in z ])

The output of this code is:

primeira vez: [(1, 'a'), (2, 'b'), (3, 'c')]
segunda vez: []

For the first time I go through all the elements of the eternal, and the second time has nothing to go through. That is why your counts result in zero, because from the second time you travel the data, has no other element, so the count is zero.

One way - not very efficient - to solve would be to put the content in a list:

data = list(zip(prefixo, status))

And in the list comprehensions you have to take the element that corresponds to the status (ie: [d[1] for d in data if d[0] == '55' and d[1] == 'assinado'].count('assinado')).

But this solution is inefficient because then you go through the same list several times, and it calls count several times (with each call from count go through the list again). Not to mention that you are putting all the contents of the file in a list (if it is too large, it will be an unnecessary waste of memory).

A better solution is to read the file line by line and update the dictionary with each line read. An example of how it would look:

def get_pais(prefixo): # não precisa do slice [:2], basta ver se começa com os dígitos
    if prefixo.startswith('55'):
        return 'P1'
    elif prefixo.startswith('56'):
        return 'P2'
    elif prefixo.startswith('52'):
        return 'P3'
    return None

paises = {}
with open('log.txt', 'r') as arquivo:
    for linha in arquivo: # lê o arquivo linha a linha
        dados = linha.rstrip('\n').split()
        if len(dados) != 2: # se a linha não tem todos os dados, vai para a próxima
            continue
        prefixo, status = dados # separa o prefixo e o status
        pais = get_pais(prefixo)

        if pais is not None: # se o país é válido
            if pais not in paises:  # se o país ainda não está no dicionário paises
                paises[pais] = { 'Total': 0, 'Ativos': 0 }
            paises[pais]['Total'] += 1
            if status == 'assinado':
                paises[pais]['Ativos'] += 1