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PROGRAM CODEBUG WITH PYTHON 3
Zap_the_rat.py
Tutorial
Language
>PYTHON
# Zap the Rat - Python3 Game for Tethered CodeBug
# Tony Goodhew - 5 Oct 2015
import codebug_tether
import time
cb = codebug_tether.CodeBug()
cb.clear()
Above The final score: seven missed opportunities to zap the rats
>STEP-02
Planning the display
The circuit will be all the outside edge LEDs, with the
rats starting their run from the bottom-left corner:
(0,0). The zap cell will be at (4,2), with a permanently
lit LED at (3,2) to mark it. Hits can be indicated by a
column of lit LEDs rising from (1,1) to (1,3). Button
‘B’ will be used to zap the rat. The final score can be
displayed with either a character ‘O’ to indicate no
missed zap opportunities - quite difficult to achieve -
or lit LEDs (0 -25) for each miss. For a ‘hit’ to register,
the button must be pressed while the zap position LED
is lit; holding the button down won't work.
>STEP-03
Setting up the CodeBug
To run the CodeBug in tethered mode, you'll
need to download and install a program called
codebug_tether.cbg. Once installed in the normal
way, the CodeBug temporarily becomes a slave device
to your Raspberry Pi and obeys instructions sent from
Python 3. (This is rather like using Nanpy to control
an Arduino from a Pi.)
Two additional Python libraries, python3-serial
and python3-codebug-tether, need to be installed
on the Pi. Point your browser to magpi.cc/1MeIWdR
and follow the excellent instructions from Thomas
Macpherson-Pope.
Open IDLE 3 and type in the Zap_the_rat.py Python
script. Save it and run it.
>STEP-04
Things to do
There are several modifications and additions you
could make to the script:
> Randomise the rat’s starting position
> Randomise the direction in which the rat runs
around the circuit
> Improve the zero final score to a square, expanding
and contracting from position (2,2) to the edge and
back again five times as a celebration.
# Circuit LED co-ordinates - round the edge from bottom-left
LEDx =(0,0,0,0,0,1,2,3,4,4,4,4,4,3,2,1)
LEDy =(0,1,2,3,4,4,4,4,4,3,2,1,0,0,0,0)
for i in range(0,-66,-1): # Display game title
cb.write_text(i,0,'Zap the Rat', direction="right")
time.sleep(0.1)
score = 0
# Rats zapped!
opps = 0
# Zap opportunities
p = 0 # Position of rat on circuit (0-15)
delay = 0.05 # Initial delay between rat moves
old_sw = 0
# Last value of switch B
running = True
# Loop control variable
cb.clear()
cb.set_pixel(3,2,1)
# Show Zap position
while running:
cb.set_pixel(LEDx[p],LEDy[p],1) # Show rat
if p == 10: opps = opps +1 # Incr opps - in (4,2)
time.sleep(delay - score * 0.007) # Wait - gets faster
sw = cb.get_input('B')
# Read switch B
pixel = cb.get_pixel(4,2) # Rat in Zap position?
cb.set_pixel(LEDx[p],LEDy[p],0) # Hide rat
if old_sw == 0 and sw == 1 and pixel == 1: # Hit?
score = score +1
# Increment hits
cb.set_pixel(1,score,1) # Show hits
if score == 3:
# Game over?
running = False
# Stop looping
p = -1
# Position of next rat
old_sw = sw
# Store switch value
p = p + 1
# Update rat position
if p > 15:
# Rat pointer out of range?
p = 0
# Reset to start position
cb.clear() # Game over - display opportunities
opps = opps - 3 # Remove successful opportunities
print("Missed Opportunities were ",opps)
if opps > 25: # Reduce missed opps to 25 max
opps = 25
if opps == 0:
cb.write_text(0,0,'O') # Zero missed opps
else:
for x in range(0,5): # Display missed opps
for y in range(0,5):
if opps > 0:
cb.set_pixel(x,y,1)
else:
cb.set_pixel(x,y,0)
opps = opps - 1
time.sleep(5)
cb.clear() # Tidy display
raspberrypi.org/magpi January 2016 49