Modules and Packages ==================== In this tutorial we will start to use vscode to develop a Python package for making buildings in the game. We will be starting with the pagoda building from the previous tutorial and here we will also go into the detail of how the ``build_pagoda`` function works. You may like to install Python extensions for vscode at this point, see `../how-to/extensions` Getting a Bash Prompt --------------------- We are going to use some bash commands here so lets open a second terminal in VSCode so that we can have a bash prompt but also keep our Python shell prompt open. Right click in the VSCode terminal area and select ``Split Terminal`` .. figure:: ../images/split_term.png :alt: split_terminal :align: center :width: 600px Splitting the Terminal You can grab the dividing line between the two terminals and drag it to the right with your mouse. This makes the Python terminal bigger and the Bash terminal smaller. Then your terminal area of VSCode should look like this: .. figure:: ../images/terminals.png :alt: split_terminal :align: center :width: 900px Python prompt and Bash prompt .. _package: Create a Package and a Module ----------------------------- A python module is simply a file with a ``.py`` extension containing Python code. A package is simply a folder (directory) that contains python modules. We are going to create a package called ``buildings`` with a single module to start with called ``build_pagoda``. Type the following commands at the bash prompt:: cd $HOME/my_world mkdir buildings cd buildings touch __init__.py code pagoda.py The steps above were: - Change working directory to ``$HOME/my_world`` which is our VSCode work folder. - Make a new directory called ``buildings``, this is our new package - Change working directory to ``buildings`` - Create an empty file called ``__init__.py`` in the ``buildings`` directory. This is a special file name that tells Python that this directory is a Python package. - Tell vscode to open a new file called ``pagoda.py`` in the editor window Now we can paste our pagoda function into the editor window and save it with Menu -> File -> Save (or Ctrl+S is a shortcut to save the current file). Use this slightly modified version of the pagoda function: .. literalinclude :: ../../src/demo/pagoda.py :language: python To try using this function you can now type the following command in the iPython prompt: .. code-block:: python from buildings.pagoda import build_pagoda build_pagoda(world.player.pos) That should build a little pagoda around your player. You can break some blocks to make a door for you to exit the pagoda! How it Works ------------ Let's take a look at all of the new things that we used in our ``build_pagoda`` function. Import ~~~~~~ .. code-block:: python from mciwb.imports import Direction, Item, get_client, polygon ``import`` allows us to access code from other modules. One of the greatest features of Python is its extensive library of built in modules. For example the maths module contains functions for doing math. e.g. .. code-block:: python from math import sqrt, cos, sin The ``polygon`` function that we used to make the pagoda is implemented using some of these math functions. Luckily, you don't need to know anything about the mathematics of polygon construction because the ``polygon`` function has done all that for you! So, ``Direction`` and ``Item`` are already familiar, we have previously used them in **iPython** without needing to import them. But we need to import them here because we are writing a new module called ``pagoda`` (in the file pagoda.py). ``import`` is the command to share code between modules and is therefore required in our new ``pagoda`` module. import is usually used at the beginning of a module and code that is imported is available to all of the code within the module. Once you become familiar with Python you will eventually be comfortable looking at online documentation to discover packages and modules you want to use and discovering the imports you need to use them. But for now it is easiest just to copy the import statements from examples like ``pagoda.py``. Comments ~~~~~~~~ At the beginning of ``build_pagoda`` we have a block comment. It uses triple quotes ``"""`` which allow you to write a block of text including line breaks that is not interpreted as Python code. Good programmers will usually add a comment block at the top of their functions and using triple quotes is the standard way to do this. Get_client ~~~~~~~~~~ Whenever we call any functions that make changes to Minecraft we need a client object. This represents a connection to our Minecraft server. (An exception to this is functions in the ``world`` object since ``world`` holds a client connection for us to save on typing) The ``get_client`` function obtains a client object for you to use. Here we assign it into the variable ``c`` and pass ``c`` to the ``polygon`` function. Advanced programmers may want to read up on how this is a thread-safe client object! see (`mcipc`). Polygon ~~~~~~~ ``polygon`` is a function that draws the outline of a polygon using blocks. It is capable of making any regular polygon and using that shape to build a tower. The parameter ``height`` tells it how many levels of the same polygon to stack on top of each other. If you want to make a circular tower then you can just pass a large number like 400 as the number of sides. In pagoda we use 4 sides to make a square pagoda. Making a Pagoda ~~~~~~~~~~~~~~~ So how does the overall function work? The caller has specified the width of the bottom of the pagoda. We use this to calculate how many levels we can make. Each level is 2 blocks narrower than the one below and so width divided by 2 should be the number of levels. We use ``integer division`` to round down to the nearest integer as we don't want to try to make half a level ``//`` is the integer division operator. Next we see that we loop over the range of levels. For our width 30 pagoda we have 15 levels and therefore ``level`` will range from 0 to 14. For each iteration of the ``for loop`` we build some walls and a balcony. The ``base`` of the walls is calculated as ``level`` * ``floor_height`` blocks above the starting ``pos``. ``floor_height`` is the default value of 4. Thus, the first floor ``base`` is 0 blocks above the starting ``pos`` (0 times 4) and each successive ``level`` is 4 blocks above the previous ``level``. .. code-block:: python polygon( client=c, center=base, height=floor_height, diameter=floor_width, sides=4, item=item, ) To create the walls we call polygon with these parameters: client is set to c: the client object needed to talk to the Minecraft server centre is set to base: the calculated starting point for the polygon height is set to floor_height: the height of the polygon (defaulted to 4) diameter is set to floor_width: the diameter of the polygon (starting at 30 for the bottom level) sides set to 4: the number of sides of the polygon, we use 4, making a square item is set to item(which was passed to ``build_pagoda``): the blocks to use for the polygon, defaulted to GOLD_BLOCK mode is set to FIllMode.REPLACE this means that all pagoda blocks replace existing blocks. You could also use FillMode.KEEP which only places blocks if the current block is Item.AIR. As we loop around the ``for loop`` we create a new polygon at each level, but the width of it is shrinking by two blocks at each level. Eventually we get to a narrow level at the top and the loop completes. Exercise: Can you work out how the balcony is being drawn on each level? look at the math used to calculate ``balcony`` and the ``polygon`` function parameters used to draw the balcony and see if you can figure out how it works. Exercise 2: I found pesky pillagers patrolling on my pagoda. A friend pointed out that you can avoid this by placing slabs on top of every surface of the pagoda. Mobs (mobile entities) won't spawn on a slab. Also you can make the slab a different material for an interesting look. You can make a pagoda with slabs on its surfaces with just two calls to the pagoda function. Can you work out how?