.. note::
    :class: sphx-glr-download-link-note

    Click :ref:`here <sphx_glr_download_generated_examples_io_create-mef.py>` to download the full example code
.. rst-class:: sphx-glr-example-title

.. _sphx_glr_generated_examples_io_create-mef.py:


=====================================================
Create a multi-extension FITS (MEF) file from scratch
=====================================================

This example demonstrates how to create a multi-extension FITS (MEF)
file from scratch using `astropy.io.fits`.

-------------------

*By: Erik Bray*

*License: BSD*

-------------------




.. code-block:: python


    import os







HDUList objects are used to hold all the HDUs in a FITS file. This
``HDUList`` class is a subclass of Python's builtin `list`. and can be
created from scratch. For example, to create a FITS file with
three extensions:



.. code-block:: python


    from astropy.io import fits
    new_hdul = fits.HDUList()
    new_hdul.append(fits.ImageHDU())
    new_hdul.append(fits.ImageHDU())







Write out the new file to disk:



.. code-block:: python


    new_hdul.writeto('test.fits')







Alternatively, the HDU instances can be created first (or read from an
existing FITS file).

Create a multi-extension FITS file with two empty IMAGE extensions (a
default PRIMARY HDU is prepended automatically if one is not specified;
we use ``overwrite=True`` to overwrite the file if it already exists):



.. code-block:: python


    hdu1 = fits.PrimaryHDU()
    hdu2 = fits.ImageHDU()
    new_hdul = fits.HDUList([hdu1, hdu2])
    new_hdul.writeto('test.fits', overwrite=True)







Finally, we'll remove the file we created:



.. code-block:: python


    os.remove('test.fits')






**Total running time of the script:** ( 0 minutes  0.116 seconds)


.. _sphx_glr_download_generated_examples_io_create-mef.py:


.. only :: html

 .. container:: sphx-glr-footer
    :class: sphx-glr-footer-example



  .. container:: sphx-glr-download

     :download:`Download Python source code: create-mef.py <create-mef.py>`



  .. container:: sphx-glr-download

     :download:`Download Jupyter notebook: create-mef.ipynb <create-mef.ipynb>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.readthedocs.io>`_