How to write a BGZF file with Biopython?

Question

[mrals89]

Hi everyone, I've read the documentation for Bio.bgzf and I'm sufficiently confused by it.

To create an example bgzf file, I've tried the following. The write method internally uses _write_block which AFAICT adds a bgzf header. The close method flushes and adds the EOF marker.

from Bio import bgzf

header="hello\nworld\somestuff"
text="an\nexample\nbody"

test=bgzf.BgzfWriter("helloworld.bgzf")
test.write(header)
test.write(text)
test.close() # works fine

But when parsing, I'm getting a ValueError when parsing the file. zcat works just fine at the command line.

infile=bgzf.BgzfReader("helloworld.bgzf")
for values in bgzf.BgzfBlocks(infile):
   print("Raw start %i, raw length %i; data start %i, data length %i" % values)
...
ValueError: A BGZF (e.g. a BAM file) block should start with b'\x1f\x8b\x08\x04', not 'hell'; handle.tell() now says 4