Output Formatting in IPython
============================

Sometimes numerical calculation results don't look too pretty:

.. code:: python

    >>> a = 7./3 m
    >>> a

:math:`2.3333333333333335 \frac{1}{\text{m}}`

IPython Magic
-------------

Using the IPython ``%precision`` magic, the displayed result can be made
prettier:

.. code:: python

    >>> %precision 1
    >>> a

:math:`2.3 \frac{1}{\text{m}}`

The magic also works for Numpy arrays:

.. code:: python

    >>> b = np.array([1.234, 3.456])
    >>> b
    array([ 1.2,  3.5])

The documentation for the ``%precision`` magic can be found here:
`link <http://ipython.readthedocs.io/en/stable/interactive/magics.html?highlight=precision#magic-precision>`__

Custom Formatting
-----------------

The ``%precision`` magic can be overridden individually for float
quantities, using the ``.format`` property of the ``PhysicalQuantity``
class. **Attention** The ``format`` property is taking Python
``formatter`` arguments.

.. code:: python

    >>> a.format # default
    ''

.. code:: python

    >>> a.format = '.3f'
    >>> a

:math:`2.333 \frac{1}{\text{m}}`


Printing Output with Quantities
-------------------------------

.. code:: python

    >>> %precision 1
    >>> a=1.23456 mm
    >>> print(a)
    1.2 mm
    >>> print("{:.3f}".format(a))
    1.235 mm
    >>> print("%s" % a)
    1.2 mm
    >>> print("%f" % a) # this returns base unit: m
    0.001235
    >>> print("%.2f" % a.mm_)
    1.23

Another way to display quantities is using the ``Latex`` function.
Unfortunately, mixing math equations and Python's ``.format()`` needs a
little trick because of the ``{}``\ brackets.

.. code:: python

    >>> from IPython.display import display, Math, Latex
    >>> def disp(str):
    >>>     display(Latex(str))
    >>> v = 1.234567 m
    >>> disp("$v_{min}$ is %s" %v)

:math:`v_{min}` is 1.2 m

.. code:: python

    >>> disp("$v_{min}$ is "+"{:.2f}".format(v))

:math:`v_{min}` is 1.23 m

.. code:: python

    >>> disp("$v_{min}$ is %s" % ("{:.2f}".format(v))) # Alternatively

:math:`v_{min}` is 1.23 m