question about list of list using python3

Question

Code:

file =open(files, 'r')
seqs = []
title = []
f = file.readlines()

for line in f:
    if line[0] == ('>'):
        title.append(line[1:-1]) 
    if line[0] != '>':
            seqs.append(line.rstrip()) 
            

final = []
for t, s in zip(title, seqs):
    final.append([t, s])

return final

I want to pair those multiple lines described in the output.

But I'm getting output which is not aligned since sequence can occupy multiple lines.

Answer 1

you could read each line if it starts with a > then you know its a new list to append a new list to the output list with this line data and an empty string to contain the next lines.

data = """>A18178 1
caccaataaaaaaacaagcttaacctaattc
>A21196 1
cggccagatcta
>A21197 1
agcttagatctggccgggg
>AX557348 1
gcggatttactcaggggagagcccagataaatggagtctgtgcgtccaca
gaattcgcacca
>AX557349 1
gcggatttactcaggggagagcccagataaatggagtctgtgcgtccaca
gaattcgcacca
>AX557350 1
tccgtgaaacaaagcggatgtaccggatttttattccggctatggggcaa
ttccccgtcgcggagcca"""

output = []
for line in data.splitlines():
    if line.startswith('>'):
        output.append([line[1:], ''])
    else:
        output[-1][-1] += line

print(output)

OUTPUT

[
  ['A18178 1', 'caccaataaaaaaacaagcttaacctaattc'], 
  ['A21196 1', 'cggccagatcta'], 
  ['A21197 1', 'agcttagatctggccgggg'], 
  ['AX557348 1', 'gcggatttactcaggggagagcccagataaatggagtctgtgcgtccacagaattcgcacca'], 
  ['AX557349 1', 'gcggatttactcaggggagagcccagataaatggagtctgtgcgtccacagaattcgcacca'], 
  ['AX557350 1', 'tccgtgaaacaaagcggatgtaccggatttttattccggctatggggcaattccccgtcgcggagcca']
]