# Given a .gb file and a locus - how to get relevant annotations in Python?

Given a .gb file and a specific locus in the genome - how can I retrieve the relevant annotations in Python (i.e., annotations that include that locus)?

I could retrieve the features using:

SeqIO.read('my_gb_file.gb', 'gb').features


and then scan them to find the relevant ones, but it feels like reinventing the wheel.

Is there a function in Biopython that does that?
Or in any other well-maintained package?

Biopython is the main package for this. It's only a few lines, so it is not reinventing the wheel. Unfortunately, this feels like a homework question, so nobody can write the code for you as per no homework policy.

But pointers are okay...

So you want to iterate across the features table (a list in Biopython) of a record and find the case where the qualifier['locus'][0] matches your query.

The things to watch out for are:

• filter by type (CDS?)
• entries where there is not key among the qualifiers, so add error catching (try: ... except Exception: pass
• the values of the qualifiers of a feature are a list. so add a [0]
• multithreading.Pool might help if speed is a worry (which it really shouldn't). Asyncio and thread are not the way (both single core).
• This is not a homework question. A list in python comes with the builtin function index. It felt to me a bit like implementing list.index, so I asked. This seems to me like an extremely common operation, so I thought it is probable that such a function already exists, and I just failed to find it. Thanks anyway for your answer! – Oren Milman Dec 21 '19 at 13:41
• Sorry, I am really bad at figuring out when it's a homework question and when it isn't... – Matteo Ferla Dec 21 '19 at 16:22
• No harm done. And clearly you did your best to help :) – Oren Milman Dec 21 '19 at 16:28