.. _exercise_grid_printer:

*********************
Grid Printer Exercise
*********************

Printing a Grid
================

(adapted from Downey, "Think Python", ex. 3.5)

Goal:
-----

Write a function that draws a grid like the following::

    + - - - - + - - - - +
    |         |         |
    |         |         |
    |         |         |
    |         |         |
    + - - - - + - - - - +
    |         |         |
    |         |         |
    |         |         |
    |         |         |
    + - - - - + - - - - +

Hints
-----


A couple features to get you started...

printing
--------

To print more than one value on a line, you can pass multiple names into the print function:

.. code-block:: python

  print('+', '-')

If you don't want a newline after something is printed, you tell Python what you want the print to end with like so:

.. code-block:: python

  print('+', end=' ')
  print('-')

The output of these statements is ``'+ -'``.

(that end parameter defaults to a newline...)

no arguments
------------

A print function with no arguments ends the current line and goes to the next line:

.. code-block:: python

    print()

simply prints and empty line.

Simple string manipulation:
---------------------------

You can put two strings together with the plus operator:

.. code-block:: ipython

  In [20]: "this" + "that"
  Out[20]: 'thisthat


This is called concatenation.

Concatenation is particularly useful if the strings have been assigned names:

.. code-block:: ipython

  In [21]: plus = '+'

  In [22]: minus = '-'

  In [23]: plus + minus + plus
  Out[23]: '+-+'

Note that you can link any number of operations together in an expression.

Multiplication of strings
-------------------------

You can also multiply strings:

.. code-block:: ipython

  In [24]: '+' * 10
  Out[24]: '++++++++++'

And combine that with plus in a complex expression:

.. code-block:: ipython

  In [29]: first_name = 'Chris'

  In [30]: last_name = 'Barker'

  In [31]: 5 * '*' + first_name +' ' + last_name + 5 * '*'
  Out[31]: '*****Chris Barker*****'

Note that there are better ways to build up complex strings -- we'll get to that later.

Now you've got what you need to print that grid...

** give it a try! **

Part 2
=======

Making it more general.

Make it a function
------------------

One of the points of writing functions is so you can write code that does similar things, but customized by the values of input parameters. So what if we want to be able to print that grid at an arbitrary size?

Write a function ``print_grid(n)`` that takes one integer argument and prints a grid just like before, *BUT* the size of the grid is given by the argument.

For example, ``print_grid(9)`` prints the grid at the top of this page.

``print_grid(3)`` would print a smaller grid::

  + - + - +
  |   |   |
  + - + - +
  |   |   |
  + - + - +


``print_grid(15)`` prints a larger grid::

    + - - - - - - - + - - - - - - - +
    |               |               |
    |               |               |
    |               |               |
    |               |               |
    |               |               |
    |               |               |
    |               |               |
    + - - - - - - - + - - - - - - - +
    |               |               |
    |               |               |
    |               |               |
    |               |               |
    |               |               |
    |               |               |
    |               |               |
    + - - - - - - - + - - - - - - - +


This problem is underspecified.  Do something reasonable.


Part 3:
=======

Even more general...

A function with two parameters
------------------------------

Write a function that draws a similar grid with a specified number of rows and columns, and with each cell a given size.

For example,  ``print_grid2(3,4)`` results in::

    + - - - - + - - - - + - - - - +
    |         |         |         |
    |         |         |         |
    |         |         |         |
    |         |         |         |
    + - - - - + - - - - + - - - - +
    |         |         |         |
    |         |         |         |
    |         |         |         |
    |         |         |         |
    + - - - - + - - - - + - - - - +
    |         |         |         |
    |         |         |         |
    |         |         |         |
    |         |         |         |
    + - - - - + - - - - + - - - - +

(three rows, three columns, and each grid cell four "units" in size)

What to do about rounding? -- you decide.

Another example: ``print_grid2(5,3)``::

    + - - - + - - - + - - - + - - - + - - - +
    |       |       |       |       |       |
    |       |       |       |       |       |
    |       |       |       |       |       |
    + - - - + - - - + - - - + - - - + - - - +
    |       |       |       |       |       |
    |       |       |       |       |       |
    |       |       |       |       |       |
    + - - - + - - - + - - - + - - - + - - - +
    |       |       |       |       |       |
    |       |       |       |       |       |
    |       |       |       |       |       |
    + - - - + - - - + - - - + - - - + - - - +
    |       |       |       |       |       |
    |       |       |       |       |       |
    |       |       |       |       |       |
    + - - - + - - - + - - - + - - - + - - - +
    |       |       |       |       |       |
    |       |       |       |       |       |
    |       |       |       |       |       |
    + - - - + - - - + - - - + - - - + - - - +

Have fun!