sequential-tar 0.0.4

Write and read tape archives (tar) sequentially.

A wrapper around tarfile which is deliberatly limited and simple. The package sequential_tar is meant to ease the writing and reading of tarfiles where the payload of the files within the tarfile is maent to go through the program’s memory. Here, only regular files can be written to a tarfile and blocks different from regular files are ignored while reading. This package is a good start when one plans to use tarfiles as containers for programs to read data from directly into their memory without seeking or the creation of temporary files.

modes

When writing the next file to the tarfile, one can set the mode to choose either text "t" or binary "b". Further a compression can be applied by adding "|gz" to the mode. In the same manner, a mode can be set when reading a file from the tarfile. This way, possible decompression and text/binary conversions can be taken care of with just a few characters in the mode parameter.

import sequential_tar as seqtar
import os
path = "test.tar"

Set the mode for each file while writing to the tarfile.

with seqtar.open(path, "w") as tar:
    tar.write(
        name="1.txt",
        payload="I am text number 1.",
        mode="wt",
    )
    tar.write(
        name="2.txt.gz",
        payload="I am text number 2.",
        mode="wt|gz",
    )
    tar.write(
        name="3.bin.gz",
        payload=b"0123456789",
        mode="wb|gz",
    )
    tar.write(
        name="4.bin",
        payload=b"123-123-123-123-123-123-123",
        mode="wb",
    )

Set the mode for each file while reading from the tarfile.

with seqtar.open(path, "r") as tar:
    item = next(tar)
    assert item.name == "1.txt"
    assert item.read(mode="rt") == "I am text number 1."

    item = next(tar)
    assert item.name == "2.txt.gz"
    assert item.read(mode="rt|gz") == "I am text number 2."

    item = next(tar)
    assert item.name == "3.bin.gz"
    assert item.read(mode="rb|gz") == b"0123456789"

    item = next(tar)
    assert item.name == "4.bin"
    assert item.read(mode="rb") == b"123-123-123-123-123-123-123"