I have to find out the size of the protein sequence, but even using the codes below, I couldn't. This first code was to find how many proteins there are in total and to find the size of the sequences.
The attached image is just to show what I want the code to search for. I don't know what is missing in the code

    arq = open("genoma9.faa")
        conteudo = arq.read()
        print(conteudo)
        fh = open("genoma9.faa")
        n= 0
        for line in fh:
            if line.startswith(">"):
                n+= 1
                print(line)
                proteins = line.count(">")
                print("Total of Proteins: " + str(proteins))

![enter image description here][1]

Trying to find this middles characters above the >WP:

Example: 

>WP_013277001.1 DNA polymerase III subunit beta [Acetohalobium arabaticum]
MQIKIDRKNFYDGIQTVRKAISSKSTLPILSGILIETQEKKLKLVGTDLELGIECRVDANIIKDGAIVLPANHLANIVRE
LPNKELELELKKDNKIEISCGLSQFKIHGSPADEYPLLPEVGSGIEYTLSQEKFQAMINRIKFATSDDESRPFLTGGLLS


  [1]: /media/images/21b38c5b-d255-4d16-8f9c-8bb33815
I think you are reinventing the wheel. There is no need to write separate code for handling biological sequences when it all exists in BioPython and can be accessed in several lines of code. What I show below could be optimized, so it is only for illustration. I suggest you save it into a file `fasta_len_and_number.py` or something like that.

    import sys
    from Bio import SeqIO
    
    # open the file specified after script name
    FastaFile = open(sys.argv[1], 'r')
    
    counter = 0 # initialize sequence counter
    for rec in SeqIO.parse(FastaFile, 'fasta'):
        counter = counter + 1 # increase sequence counter
        name = rec.id # sequence header
        seq = rec.seq # protein/DNA sequence
        seqLen = len(rec) # determine sequence length
        print(seqLen, name) # print the length + header
    
    print('\n A total of %d sequences' % counter)
    FastaFile.close()

Running this line:

    python fasta_len_and_number.py genoma9.faa

will make hopefully a desired output. On one of my files when I tested, the last 10 lines look like this:

    130 2HY5_A
    114 2Q68_A
    141 4CDL_A
    47 6O3S_A
    12 4AKT_C
    37 4Z80_C
    145 1Y23_A
    215 6S5A_L
    
     A total of 112217 sequences

     