***********************************************
Formats for floating point values in text files
***********************************************

.. testsetup::

    import numpy as np
    # Set print options for doctests below
    np.set_printoptions(precision=6)

Let's say we have a floating point numbers like this:

>>> a_number = 314.15926
>>> a_number
314.15926

We can also represent these numbers in exponential format.  Exponential format
breaks the number into a two parts: the *significand*; and the *exponent*.

The significand is a floating point number with one digit before a decimal
point.  The exponent is an integer.  For example:

>>> exp_number = 3.1415926E2
>>> exp_number
314.15926

Here the significand is ``3.1415926``, and the exponent is ``2``, the value
after the ``E``.  The number is given by ``s * 10 ** e`` where ``s`` is the
significand and ``e`` is the exponent.  In this case: ``314.15926 = 3.1415926
* 10 ** 2``.

This exponential format is the default format that ``np.savetxt`` uses to
represent floating point numbers when writing to text files.  For example:

>>> import numpy as np
>>> an_array = np.array([a_number, 1.0, 2.0])
>>> an_array
array([ 314.15926,    1.     ,    2.     ])
>>> np.savetxt('some_numbers.txt', an_array)
>>> with open('some_numbers.txt', 'rt') as fobj:
...     contents = fobj.read()
>>> print(contents)
3.141592600000000175e+02
1.000000000000000000e+00
2.000000000000000000e+00
<BLANKLINE>

.. testcleanup::

    import os
    os.unlink('some_numbers.txt')