So i'm working on a segment of a pipeline using biopython, where i'll taking in fasta files with any number of sequences and running blast searches then parsing the results for passing to multiseq alignment.

I'm wondering if there is a way i can limit the number of sequences taken from the files for each search e.g. i blast search the sequences in batches of 20.

Is there a way i can do this without segmenting the large fasta files or is this the best option?