Converting sequence files
Many bioinformatics tools take different input file formats, so there is a common need to interconvert between sequence file formats. One useful option is the commandline tool seqret from EMBOSS, but here we'll show how to tackle this problem with Bio.SeqIO.
Suppose you have a GenBank file which you want to turn into a Fasta file. For example, lets consider the file 'cor6_6.gb' (which is included in the Biopython unit tests under the GenBank directory):
from Bio import SeqIO input_handle = open("cor6_6.gb", "rU") output_handle = open("cor6_6.fasta", "w") sequences = SeqIO.parse(input_handle, "genbank") count = SeqIO.write(sequences, output_handle, "fasta") output_handle.close() input_handle.close() print "Coverted %i records" % count
In this example the GenBank file contained six records and started like this:
LOCUS ATCOR66M 513 bp mRNA PLN 02-MAR-1992 DEFINITION A.thaliana cor6.6 mRNA. ACCESSION X55053 VERSION X55053.1 GI:16229 ...
The resulting Fasta file also contains all six records and looks like this:
>X55053.1 A.thaliana cor6.6 mRNA. AACAAAACACACATCAAAAACGATTTTACAAGAAAAAAATA... ...
Note that all the Fasta file can store is the identifier, description and sequence.
By changing the format strings, that code could be used to convert between any supported file formats.
You don't have to work with file handles - see this example using stdin and stdout pipes with Bio.SeqIO.
How it works
See the Bio.SeqIO page.