def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def test_ccode_Pow():
    assert ccode(x**3) == "pow(x, 3)"
    assert ccode(x**(y**3)) == "pow(x, pow(y, 3))"
    assert ccode(1/(g(x)*3.5)**(x - y**x)/(x**2 + y)) == \
        "pow(3.5*g(x), -x + pow(y, x))/(pow(x, 2) + y)"
    assert ccode(x**-1.0) == '1.0/x'
    assert ccode(x**Rational(2, 3)) == 'pow(x, 2.0L/3.0L)'
    _cond_cfunc = [(lambda base, exp: exp.is_integer, "dpowi"),
                   (lambda base, exp: not exp.is_integer, "pow")]
    assert ccode(x**3, user_functions={'Pow': _cond_cfunc}) == 'dpowi(x, 3)'
    assert ccode(x**3.2, user_functions={'Pow': _cond_cfunc}) == 'pow(x, 3.2)'