CSC111 Lab 7 2015

--D. Thiebaut (talk) 11:09, 8 March 2015 (EDT)

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In this lab you will play with a graphics library that will allow you to draw simple shapes on the screen.

Setup for Graphics

Step 1: Download the graphics.py Library

• Copy/Paste the code from this page to Idle and save it in the directory where you will save your programs for Week 7, under the name graphics.py.

Step 2: Testing your installation

• While graphics.py is in your Idle window, simply run your progrma.
• If everything goes well, you should see this simple window appear on your screen:

• Click a few times on the window and verify that the window responds by changing the color or size of various graphic objects.

Graphics programs have to be run from Idle to work correctly, and need the graphics.py library distributed by Zelle, the author of our textbook.

Download graphics.py

First, Login to the Mac with your 111c-xx account, and then follow the steps below, referring to the image above

1. Open the Finder window, then the Utilities folder, then click on X11
2. This opens the white XTerm window in the top left. We won't use it, but it needs to be running for the graphics to work. You can iconize this xterm window to clean up your desktop, though.
3. Use the same steps (Finder --> Utilities) and open a Terminal window.
4. A new black window opens up.
5. In it, type the following commands:
   
   ssh -Y 111c-xx@beowulf.csc.smith.edu (You may have to type yes to confirm)
   
   getcopy graphics.py
   
   python graphics.py
   
   
6. If everything goes well, you should see the small gray window with a triangle and a rectangle, with the words Centered Text.

Question 8

Open Python in interactive mode, and try the various graphics functions, as illustrated in Section 5.3 of Zelle's textbook:

  >>> from graphics import *
  >>> win = GraphWin( "Lab 5 Demo" )
  >>> center = Point( 100, 100 )
  >>> circ = Circle( center, 30 )
  >>> circ.setFill( 'red' )
  >>> circ.draw( win )
  >>> label = Text( center, "red circle" )
  >>> label.draw( win )
  >>> rect = Rectangle( Point( 30, 30 ), Point( 70, 70 ) )
  >>> rect.draw( win )
  >>> win.close()

Using this bit of knowledge, could you generate this figure?

The sections below are optional, and intended for those who are interested in writing graphics programs directly on their laptop computers without being connected to Beowulf.

Installing the Graphics Package on your laptop (Optional)

Use these directions if you would like to have python and the graphics library installed on your own computer.

Directions for Windows laptops

(These directions were inspired by directions posted at the Rose-Hulman Institute of Technology)

Python

First, Install Python 2.6 on your machine, if you haven't already done so.

• Logon as an adminstrator if you have a regular user account and an administrator account for your laptop (most people use the same for both).
• Download Python (it's free!). Visit http://www.python.org/download/ and select the Python 2.6.2 Windows installer.
• Run the installer, installing it in C:\Program Files\Python26\ (vs. the default, which is C:\Python26 ). The other defaults are fine to use.
• Change the directory that the Python development environment, IDLE, starts in when loading and saving files. (By default it looks for and saves files in the program directory.)
  • Log into your regular user account if it is different from your administrator account.
  • Click on Start → All Programs → Python 2.6
  • Right-click on IDLE (Python GUI) and choose Properties
  • Change the Start in: field to point to the place where you want to keep Python program files. A good choice might be C:\Documents and Settings\yourname\My Documents\PythonFiles. (An easy way to get that path name: Open My Documents and browse to the folder. Select the pathname in the Address bar; Copy. Go back to the Idle Properties Window, and Paste into the Start In field.) Whatever folder you decide to use, you will need to use Windows Explorer to create it if it does not exist.

Then load the Zelle Graphics library

• Download this file graphics.py.
• Save the file graphics.py in the directory C:\Program Files\Python26\Lib\site-packages

Potential “gotchas”: (1) That is Lib, not libs, in the path. (2) if you installed Python in a different location than C:\Program Files\Python26, you’ll need to find your Python26\Lib\site-packages folder.

To verify your installation

• Launch IDLE by clicking Start → All Programs → Python 2.6 → IDLE (Python GUI)
• At the prompt type:

 from graphics import *

if you do not get an error message, then the installation was successful.

Directions for Mac laptops

• Use Finder to create a new folder in your favorite spot. For example you can create a folder called CSC111 on your Desktop.
• Download this file graphics.py, and unzip it. Put grahpics.py in the directory (folder) you created above.
• Open a terminal window, and type the following commands:

 cd
 cd Desktop
 cd CSC111            (or whatever directory you decided to create)
 emacs testgraphics.py

• create the following python program:

from graphics import *
def main():
    test()

main()

• Run it!

  python testgraphics.py

• You should get this new window on your screen: