I want to create a script for unzip (.tar.gz) file via (Python)

Why do you want to “press” twice to extract a .tar.gz, when you can easily do it once? Here is a simple code to extract both .tar and .tar.gz in one go:

import tarfile

if fname.endswith("tar.gz"):
    tar = tarfile.open(fname, "r:gz")
    tar.extractall()
    tar.close()
elif fname.endswith("tar"):
    tar = tarfile.open(fname, "r:")
    tar.extractall()
    tar.close()