fasta_lake.gzip_io

fasta_lake.gzip_io

Deterministic gzip writing.

gzip.open stamps the current wall-clock time into the 4-byte MTIME field of the gzip header and the file's basename into FNAME, so two runs that produce identical content produce different bytes. Every receipt in this package hashes its outputs, so that timestamp made identical reruns look different. Writers here set MTIME to 0 and omit FNAME.

open_gzip_text

open_gzip_text(path: str | Path, newline: str = '', encoding: str = 'utf-8')

Open path for writing gzip-compressed text with a zero MTIME header.

Source code in fasta_lake/gzip_io.py

@contextmanager
def open_gzip_text(path: str | Path, newline: str = "", encoding: str = "utf-8"):
    """Open ``path`` for writing gzip-compressed text with a zero MTIME header."""
    with (
        open(path, "wb") as raw,
        gzip.GzipFile(filename="", mode="wb", fileobj=raw, mtime=0) as compressed,
        io.TextIOWrapper(compressed, encoding=encoding, newline=newline) as text,
    ):
        yield text