Python - Match patterns, print pattern and n lines after it

Question

I have a file like this (with +10000 sequences, +98000 lines):

>DILT_0000000001-mRNA-1
MKVVKICSKLRKFIESRKDAVLPEQEEVLADLWAFEGISEFQMERFAKAAQCFQHQYELA
IKANLTEHASRSLENLGRARARLYDYQGALDAWTKRLDYEIKGIDKAWLHHEIGRAYLEL
NQYEEAIDHAATARDVADREADMEWDLNATVLIAQAHFYAGNLEEAKVYFEAAQNAAFRK
GFFKAESVLAEAIAEVDSEIRREEAKQERVYTKHSVLFNEFSQRAVWSEEYSEELHLFPF
AVVMLRCVLARQCTVHLQFRSCYNL
>DILT_0000000101-mRNA-1
MSCRRLSMNPGEALIKESSAPSRENLLKPYFDEDRCKFRHLTAEQFSDIWSHFDLDGVNE
LRFILRVPASQQAGTGLRFFGYISTEVYVHKTVKVSYIGFRKKNNSRALRRWNVNKKCSN
AVQMCGTSQLLAIVGPHTQPLTNKLCHTDYLPLSANFA
>DILT_0001999301-mRNA-1
LEHGIQPDGQMPSDKTIGGGDDSFQTFFSETGAGKHVPRAVMVDLEPTVIGEYLCVLLTS
FILFRLISTNLGPNSQLASRTLLFAADKTTLFRLLGLLPWSLLKIAVQ
>DILT_0001999401-mRNA-1
MAENGEDANMPEEGKEGNTQDQGEHQQDVQSDEPNEADSGYSSAASSDVNSQTIPITVIL
PNREAVNLSFDPNISVSELQERLNGPGITRLNENLFFTYSGKQLDPNKTLLDYKVQKSST
LYVHETPTALPKSAPNAKEEGVVPSNCLIHSGSRMDENRCLKEYQLTQNSVIFVHRPTAN
TAVQNREEKTSSLEVTVTIRETGNQLHLPINPHXXXXTVEMHVAPGVTVGDLNRKIAIKQ

all the lines with the '>' are IDs. The following lines are the sequences regarding the ID.

I also have a file with the IDs of the sequences I want, like:

DILT_0000000001-mRNA-1
DILT_0000000101-mRNA-1
DILT_0000000201-mRNA-1
DILT_0000000301-mRNA-1
DILT_0000000401-mRNA-1
DILT_0000000501-mRNA-1
DILT_0000000601-mRNA-1
DILT_0000000701-mRNA-1
DILT_0000000801-mRNA-1
DILT_0000000901-mRNA-1

I want to write a script to match the ids and copy the sequences of this IDs, but I'm just getting the IDs, without the sequences.

seqs = open('WBPS10.protein.fa').readlines()
ids = open('ids.txt').readlines()

for line in ids:
    for record in seqs:
        if line == record[1:]:
            print record

I don't know what to write to get the 'n' lines after the ID, because sometimes it's 2 lines, other sequences have more as you can see in my example.

The thing is, I'm trying to do it without using Biopython, which would be a lot easier. I just want to learn other ways.

Answer 1

seqs_by_ids = {}
with open('WBPS10.protein.fa', 'r') as read_file:
    for line in read_file.readlines():
        if line.startswith('>'):
            current_key = line[1:].strip()
            seqs_by_ids[current_key] = ''
        else:
            seqs_by_ids[current_key] += line.strip()

ids = set([line.strip() for line in open('ids.txt').readlines()])

for id in ids:
    if id in seqs_by_ids:
        print(id)
        print('\t{}'.format(seqs_by_ids[id]))

output:

DILT_0000000001-mRNA-1
    MKVVKICSKLRKFIESRKDAVLPEQEEVLADLWAFEGISEFQMERFAKAAQCFQHQYELAIKANLTEHASRSLENLGRARARLYDYQGALDAWTKRLDYEIKGIDKAWLHHEIGRAYLELNQYEEAIDHAATARDVADREADMEWDLNATVLIAQAHFYAGNLEEAKVYFEAAQNAAFRKGFFKAESVLAEAIAEVDSEIRREEAKQERVYTKHSVLFNEFSQRAVWSEEYSEELHLFPFAVVMLRCVLARQCTVHLQFRSCYNL
DILT_0000000101-mRNA-1
    MSCRRLSMNPGEALIKESSAPSRENLLKPYFDEDRCKFRHLTAEQFSDIWSHFDLDGVNELRFILRVPASQQAGTGLRFFGYISTEVYVHKTVKVSYIGFRKKNNSRALRRWNVNKKCSNAVQMCGTSQLLAIVGPHTQPLTNKLCHTDYLPLSANFA