Difference between revisions of "CSC111 Lab 8 2015"

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Line 84: Line 84:
 
<br />
 
<br />
 
::<source lang="python">
 
::<source lang="python">
 +
# createFile: creates a text file containing a haiku followed by the line <<<END>>>
 +
# followed by some text about the source of the haiku and the rights of use.
 
def createFile( fileName ):
 
def createFile( fileName ):
 +
 +
    # open the file
 
     file = open( fileName, "w" )
 
     file = open( fileName, "w" )
 +
 +
    # write some text
 
     file.write("""
 
     file.write("""
    Haikus from http://www.toyomasu.com/haiku/
 
 
     An old pond!
 
     An old pond!
 
     A frog jumps in-
 
     A frog jumps in-
 
     The sound of water.
 
     The sound of water.
 
     <<<END>>>
 
     <<<END>>>
 +
    Haikus from http://www.toyomasu.com/haiku/
 
     Feel free to use anything from this page as
 
     Feel free to use anything from this page as
 
     long as you make references and links to HAIKU
 
     long as you make references and links to HAIKU
Line 97: Line 103:
 
     Edited by Kei Grieg Toyomasu,
 
     Edited by Kei Grieg Toyomasu,
 
     kei at toyomasu dot com""" )
 
     kei at toyomasu dot com""" )
 +
 +
    # close the file
 
     file.close()
 
     file.close()
  

Revision as of 13:48, 22 March 2015

--D. Thiebaut (talk) 14:10, 22 March 2015 (EDT)


<showafterdate after="20150325" before="20150601">

Part 1: While Loops


Exercise 1: Robust Input with While


def getPositiveNumber():
    #
    # put your code here
    #
    return 10   # just to make sure the code is accepted by Idle


def main():

    # Part 1, Exercise 1
    x = getPositiveNumber()
    print( "getPositiveNumber() returned", x )

main()


Complete the function getPositiveNumber() so that it asks the user for a number larger than 0, and keeps on prompting the user as long as she doesn't enter a valid number.

Below is an example of the interaction between computer and user.

Please enter a number greater than 0: -1
-1 is invalid.
Please enter a number greater than 0: -3
-3 is invalid.
Please enter a number greater than 0: 0
0 is invalid.
Please enter a number greater than 0: 20
getPositiveNumber() returned 20
>>>


Exercise 2: Ask for Yes/No answer


Same idea as in Exercise 1, but this time the new function, called getYesNo() will keep on asking a question until the user's input is "YES", "yes", "y", "NO", "no", or "n". Any combination of lower/upper case in the spelling is accepted ("yES" is valid).

Source


def getYesNo():
    #
    # put your code here
    #
    return "Y"    # just to make sure the code works as is.
            
def main():
    # Part1, Exercise 2
    likesChoco = getYesNo()
    if likesChoco in ["YES", "Y" ]:
        print( "Me too!" )
    else:
        print( "Sorry to hear that!" )
        
main()


Example output


Do you like chocolate (Y/N)? possibly
please enter by 'Yes' or 'No'

Do you like chocolate (Y/N)? I don't know
please enter by 'Yes' or 'No'

Do you like chocolate (Y/N)? Oui
please enter by 'Yes' or 'No'

Do you like chocolate (Y/N)? y
Me too!


Exercise 3: While Loop and Reading File


# createFile: creates a text file containing a haiku followed by the line <<<END>>>
# followed by some text about the source of the haiku and the rights of use.
def createFile( fileName ):

    # open the file
    file = open( fileName, "w" )

    # write some text
    file.write("""
    An old pond!
    A frog jumps in-
    The sound of water.
    <<<END>>>
    Haikus from http://www.toyomasu.com/haiku/
    Feel free to use anything from this page as
    long as you make references and links to HAIKU
    for PEOPLE. Last updated: Jan 10th. 2001.
    Edited by Kei Grieg Toyomasu,
    kei at toyomasu dot com""" )

    # close the file
    file.close()

def readFileTillMarker( fileName ):
    #
    # add your code here
    #
    return []   # just to make sure the code compiles. 

def main():
    # Part 1, Exercise 3
    # create a sample text file for testing.  The file will contain the string <<<END>>>
    # in it.
    createFile( "lab8Demo.txt" )

    # get all the lines before but not including <<<END>>>
    lines = readFileTillMarker( "lab8Demo.txt" )

    # display the lines returned.  We strip them to remove the extra \n at the end and
    # the extra spaces at the front of each line.
    print( "Lines found by readFileTillMarker(): " )
    for line in lines:
        print( line.strip() )


Same idea as the previous 2 exercises. This time you need to add code to the function readFileTillMarker() so that it will read all the lines contained in the file whose name is passed as a parameter, and that appear before the marker string <<<END>>>. In other words, the function reads the lines, adds them to a list of lines, until it finds a line containing the string <<<END>>>. It returns a list of all the lines read.

The function createFile() creates a simple file you can use for testing. Take a look at it. R </showafterdate>