Extract only a single directory from tar

Question

I am working on a project in python in which I need to extract only a subfolder of tar archive not all the files. I tried to use

tar = tarfile.open(tarfile)
tar.extract("dirname", targetdir)

But this does not work, it does not extract the given subdirectory also no exception is thrown. I am a beginner in python. Also if the above function doesn't work for directories whats the difference between this command and tar.extractfile() ?

Answer 1

Building on the second example from the tarfile module documentation, you could extract the contained sub-folder and all of its contents with something like this:

with tarfile.open("sample.tar") as tar:
    subdir_and_files = [
        tarinfo for tarinfo in tar.getmembers()
        if tarinfo.name.startswith("subfolder/")
    ]
    tar.extractall(members=subdir_and_files)

This creates a list of the subfolder and its contents, and then uses the recommended extractall() method to extract just them. Of course, replace "subfolder/" with the actual path (relative to the root of the tar file) of the sub-folder you want to extract.

Answer 2

The other answer will retain the subfolder path, meaning that subfolder/a/b will be extracted to ./subfolder/a/b. To extract a subfolder to the root, so subfolder/a/b would be extracted to ./a/b, you can rewrite the paths with something like this:

def members(tf):
    l = len("subfolder/")
    for member in tf.getmembers():
        if member.path.startswith("subfolder/"):
            member.path = member.path[l:]
            yield member

with tarfile.open("sample.tar") as tar:
    tar.extractall(members=members(tar))