Split fasta into multiple fasta files with a max size

SPLIT-FASTA.py

#!/usr/bin/env python
'''
split fasta file into multiple smaller fasta files

Use like this:

python SPLIT-FASTA.py fasta-name.fa output-prefix SIZE

So if your input fasta was contigs.fa, and had 190 sequences then:

python SPLIT-FASTA.py contigs.fa contigs-mini 50

would result in four output files:
contigs-mini_0.fa
contigs-mini_1.fa
contigs-mini_2.fa
contigs-mini_3.fa
'''

import sys
import anvio.fastalib as f

input_file_name = sys.argv[1]
output_file_prefix = sys.argv[2]
max_number_per_file = int(sys.argv[3])

c = f.ReadFasta(f_name= input_file_name)

n = 0
m = 0
output_file_name = '%s_%s.fa' % (output_file_prefix, m)
output_fasta = f.FastaOutput(output_file_path=output_file_name)
for header,seq in zip(c.ids, c.sequences):
    if n == max_number_per_file:
        n = 0
        m += 1
        output_fasta.close()
        output_file_name = '%s_%s.fa' % (output_file_prefix, m)
        output_fasta = f.FastaOutput(output_file_path=output_file_name)
    n += 1
    output_fasta.write_id(header)
    output_fasta.write_seq(seq)
output_fasta.close()