Tutorial Moodle VPL Chessboard -- Python

--D. Thiebaut (talk) 17:00, 11 June 2014 (EDT)

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This tutorial illustrates how to setup a VPL activity that evaluates a python program that

1. prompts the user for an integer N
2. display an NxN chessboard of alternating cells on stdout.

This VPL activity uses an extra python program to filter out extra information from the output.

Example User Interaction

Here is an example of the interaction of the user program:

Please enter dimension of board: 8
###...###...###...###...
###...###...###...###...
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VPL Activity Description

Chessboard

Due date: Sunday, 19 June 2016, 8:00 PM
Requested files: chessboard.py (Download)
Type of work: Individual work
Grade settings: Maximum grade: 100
Run: Yes Evaluate: Yes
Automatic grade: Yes
prints a 2-dimensional chessboard
Requested files

chessboard.py

# put your code here

Execution files

vpl_run.sh

#! /bin/bash
 
echo "#! /bin/bash"  > vpl_execution
echo "python3.4 runChessboard.py" >> vpl_execution
chmod +x vpl_execution

vpl_evaluate.cases

case = Test 1
input = 0
output = "
"
 
case = Test 2
input = 1
output = "###
###
###
"
case = Test 3
input = 8 
output = "###...###...###...###...
###...###...###...###...
###...###...###...###...
...###...###...###...###
...###...###...###...###
...###...###...###...###
###...###...###...###...
###...###...###...###...
###...###...###...###...
...###...###...###...###
...###...###...###...###
...###...###...###...###
###...###...###...###...
###...###...###...###...
###...###...###...###...
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###...###...###...###...
###...###...###...###...
###...###...###...###...
...###...###...###...###
...###...###...###...###
...###...###...###...###
"

runChessboard.py

#runChessboard.py
import sys

#--- get dimension of chessboard
N = input( "" )

#--- put N in a text file that will be used as stdin for chessboard.py 
file = open( "fakestdin.txt", "w" )
file.write( N+"\n" )
file.close()

#--- make stdin read information from the text file
sys.stdin = open( "fakestdin.txt", "r" )

#--- capture the stdout of the program to test into a file
saveStdOut = sys.stdout
sys.stdout = open( "fakestdout.txt", "w" )

#--- run the program to test ---
import chessboard

#--- filter out junk from output of program ---
sys.stdout.close()
sys.stdout = saveStdOut
file = open( "fakestdout.txt", "r" )
text = file.read()
index = text.find( "#" )
text = text[index:]
text = text.strip( ).strip( "\n" ) + "\n"
print( text, end="" )
file.close()

This concludes this tutorial