Tutorial Moodle VPL Chessboard -- Python

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

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Moodle VPL Tutorials

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This tutorial builds on the first one in the series, which should be done first, as the present tutorial skips some steps. Here we illustrate 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 additional python program to filter out extra information from the output of the student program.

Setup

• Moodle Version 2.7 + (Build: 20140529)
• VPL Version 3.0.1
• For details on how Moodle and VPL were installed, go to this page.

Example of User Interaction

Here is are examples of interactions with the solution program:

Please enter dimension of board: 0

(no output from the program)

Please enter dimension of board: 8
###...###...###...###...
###...###...###...###...
###...###...###...###...
...###...###...###...###
...###...###...###...###
...###...###...###...###
###...###...###...###...
###...###...###...###...
###...###...###...###...
...###...###...###...###
...###...###...###...###
...###...###...###...###
###...###...###...###...
###...###...###...###...
###...###...###...###...
...###...###...###...###
...###...###...###...###
...###...###...###...###
###...###...###...###...
###...###...###...###...
###...###...###...###...
...###...###...###...###
...###...###...###...###
...###...###...###...###

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 = "###...###...###...###...
###...###...###...###...
###...###...###...###...
...###...###...###...###
...###...###...###...###
...###...###...###...###
###...###...###...###...
###...###...###...###...
###...###...###...###...
...###...###...###...###
...###...###...###...###
...###...###...###...###
###...###...###...###...
###...###...###...###...
###...###...###...###...
...###...###...###...###
...###...###...###...###
...###...###...###...###
###...###...###...###...
###...###...###...###...
###...###...###...###...
...###...###...###...###
...###...###...###...###
...###...###...###...###
"

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()

Testing

• Click on VPL administration, then Test activity. Enter the program below in the chessboard.py program area, and Evaluate.

def printBlock( visible ):
    
    if visible==True:
        print( "###", end="" )
    else:
        print( "...", end="" )


# Makes indicated number of 3x3 cell(s) and alternates
# black (###) and white (...) cells for each row
def printLine( visibility, isOdd, dimension ):

    for i in range( 3 ):
        for i in range( dimension//2 ):
            printBlock( visibility )
            printBlock( not visibility )
        
        if isOdd:
            printBlock( visibility )

        print()


# Alternates black (###) and white (...) cells the number of
# times that the user indicated for each column
def repeatLine( dimension, isOdd ):

    for i in range( dimension//2 ):
        printLine( True, isOdd, dimension )
        printLine( False, isOdd, dimension )

    if isOdd:
        printLine( True, isOdd, dimension )


def main():
    # Asks user for dimension of chessboard
    dimension = int( input( "Enter dimension of board: " ) )

    # Asks user again for another input
    # if user enters negative number
    while dimension < 0:
        dimension = int( input( "Invalid input. Please enter 0 or positive number: " ) )

    # Boolean variable when dimension is
    # odd for the for loops in functions
    isOdd = dimension % 2 == 1

    # prints chessboard
    repeatLine( dimension, isOdd )


main()

• Verify that the submitted program gets a 100 mark for all 3 tests.

This concludes this tutorial