def test_method_lookup(self):
        # Issue #18879: Looking up a temporary file method should keep it
        # alive long enough.
        f = self.do_create()
        wr = weakref.ref(f)
        write = f.write
        write2 = f.write
        del f
        write(b'foo')

class _TemporaryFileCloser:
    """A separate object allowing proper closing of a temporary file's
    underlying file object, without adding a __del__ method to the
    temporary file."""

    cleanup_called = False
    close_called = False

    def __init__(self, file, name, delete=True, delete_on_close=True):
        self.file = file
        self.name = name
        self.delete = delete
        self.delete_on_close = delete_on_close

    def cleanup(self, windows=(_os.name == 'nt'), unlink=_os.unlink):
        if not self.cleanup_called:
            self.cleanup_called = True
            try:
                if not self.close_called:
                    self.close_called = True
                    self.file.close()
            finally:
                if self.delete and not (self.delete_on_close and windows):
                    try:
                        unlink(self.name)
                    except FileNotFoundError:
                        pass

    def close(self):
        if not self.close_called:
            self.close_called = True
            try:
                self.file.close()
            finally:
                if self.delete and self.delete_on_close:
                    self.cleanup()

    def __del__(self):
        self.cleanup()

class _TemporaryFileWrapper:
    """Temporary file wrapper

    This class provides a wrapper around files opened for
    temporary use.  In particular, it seeks to automatically
    remove the file when it is no longer needed.
    """

    def __init__(self, file, name, delete=True, delete_on_close=True):
        self.file = file
        self.name = name
        self._closer = _TemporaryFileCloser(file, name, delete,
                                            delete_on_close)

    def __getattr__(self, name):
        # Attribute lookups are delegated to the underlying file
        # and cached for non-numeric results
        # (i.e. methods are cached, closed and friends are not)
        file = self.__dict__['file']
        a = getattr(file, name)
        if hasattr(a, '__call__'):
            func = a
            @_functools.wraps(func)
            def func_wrapper(*args, **kwargs):
                return func(*args, **kwargs)
            # Avoid closing the file as long as the wrapper is alive,
            # see issue #18879.
            func_wrapper._closer = self._closer
            a = func_wrapper
        if not isinstance(a, int):
            setattr(self, name, a)
        return a

    # The underlying __enter__ method returns the wrong object
    # (self.file) so override it to return the wrapper
    def __enter__(self):
        self.file.__enter__()
        return self

    # Need to trap __exit__ as well to ensure the file gets
    # deleted when used in a with statement
    def __exit__(self, exc, value, tb):
        result = self.file.__exit__(exc, value, tb)
        self._closer.cleanup()
        return result

    def close(self):
        """
        Close the temporary file, possibly deleting it.
        """
        self._closer.close()

    # iter() doesn't use __getattr__ to find the __iter__ method
    def __iter__(self):
        # Don't return iter(self.file), but yield from it to avoid closing
        # file as long as it's being used as iterator (see issue #23700).  We
        # can't use 'yield from' here because iter(file) returns the file
        # object itself, which has a close method, and thus the file would get
        # closed when the generator is finalized, due to PEP380 semantics.
        for line in self.file:
            yield line

    except:
        if name is not None and not (
          _os.name == 'nt' and delete and delete_on_close):
            _os.unlink(name)
        raise

class _TemporaryFileCloser:

   # these are class attributes
    cleanup_called = False
    close_called = False

    def __init__(self, file, name, delete=True, delete_on_close=True):
        self.file = file
        self.name = name
        self.delete = delete
        self.delete_on_close = delete_on_close

        # why not just setting the default  instance attributes here?
        # cleanup_called = False
        # close_called = False

    def cleanup(self, windows=(_os.name == 'nt'), unlink=_os.unlink):
        if not self.cleanup_called:        #if done, 1st time, this is looks at class attribute
            # But this creates an instance attribute with the same name
            # From now on all calls to  self.cleanup_called will return an instance attribute 
            self.cleanup_called = True