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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_python_cmd(self):
 """ return the python executable in the virtualenv. Try first sys.executable but use fallbacks. """

        file_names = ["pypy.exe", "python.exe", "python"]
        executable = sys.executable
        if executable is not None:
            executable = os.path.split(executable)[1]
            file_names.insert(0, executable)

        return self._get_bin_file(*file_names)