Difference between revisions of "CSC111 Lab 5 2015b Part 2"
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Revision as of 16:47, 6 October 2015
--D. Thiebaut (talk) 16:10, 6 October 2015 (EDT)
Contents
Preparation For Processing Files
- Copy paste the program below in a new Idle window, and call it lab5Companion.py.
- Save your new program to your working directory, where you normally save your lab programs.
- Run the program. It should create 3 text files in your folder. You will be using them in this lab. The files are called:
- chocoQuotes.txt
- hargitay.txt
- joanneHarris.txt
[19:14:51] ~/Desktop/temp$: cat lab5prep.py # lab5Companion.py # D. Thiebaut # This program will create several files in the directory # where you will run it. # The files are retrieved from a Web server, stored temporarily # in a string, and stored in a local file on your disk. # The 3 files are very, very short. # Their names are: # - chocoQuotes.txt # - hargitay.txt # - joanneHarris.txt import urllib.request # the lib that handles the url stuff # main program def main(): # list of files to retrieve URLs = [ "http://cs.smith.edu/~dthiebaut/111/files/chocoQuotes.txt", "http://cs.smith.edu/~dthiebaut/111/files/hargitay.txt", "http://cs.smith.edu/~dthiebaut/111/files/joanneHarris.txt" ] # get each file, one at a time for url in URLs: # fetch the file and put its contents in the # string text. response = urllib.request.urlopen( url ) text = response.read().decode( 'UTF-8' ) # write text to file, in the same directory as this program. fileName = url.split( "/" )[-1] file = open( fileName, "w" ) file.write( text + "\n" ) file.close() # give feedback to user. print( "File {0:1} created in your folder".format( fileName ) ) main()
Reading Text From File
- Open Finder or Windows Explorer and go to the folder that contains your lab5.py program, as well as your lab5Companion.py programs. Make sure the folder contains the 3 text files you created earlier.
- Open the file name hargitay.txt. Verify that it contains the same poem we have been playing with.
- Either create a new program or add a new main() function to your existing program (rename the original main, main2(), maybe?), and put the code below in the new function:
def main(): fileName = "hargitay.txt" file = open( fileName, "r" ) lines = file.readlines() file.close() for line in lines: print( line )
- Run the program. Observe its output.
- The reason for the double-spacing is that each line read from the file contains a '\n' at the end of it. And when you print such a line, the print() function adds its own \n at the end. This is why you get a blank line in between lines.
- One way to remove the '\n' at the end of each line is to print the line as follows: print( line.rstrip() ). The rstrip() method right-strips the string of all white-space characters, which include spaces, tabs, and '\n'-characters.
Challenge #4 |
- Make your program get the name of the file from the user, with an input() statement.
- Then, make your program output the contents of the file in a box.
- Test your program by providing it with different file names:
- hargitay.txt
- joanneHarris.txt
- chocoQuotes.txt
- Adjust the width of the box if necessary.
Challenge #5 |
- Exact same challenge as Challenge 3, but this time start with this program, where I have replaced the .readlines() method with .read().
def main(): fileName = input( "File name? " ) file = open( fileName, "r" ) text = file.read() file.close() print( "The type of text is", type( text ) ) print( "text = ", text )
- Note
- when Python says that something is of type <class 'str'>, it means that it is a string.
Writing Text to File
- Try this new version of main:
def main(): fileName = "hargitay.txt" file = open( fileName, "r" ) text = file.read() file.close() text = text.replace( "chocolate", "carrot" ) text = text.replace( "Chocolate", "Carrot" ) file = open( fileName, "w" ) file.write( text + "\n" ) file.close()
- Open Finder or Windows Explorer, and take a look at the file "hargitay.txt", either with TextEdit or with Notepad. See anything different?
- BTW, You can recreate the original file by running the lab5Companion.py program again.
Challenge #6 |
- Modify the program so that it prompts the user for
- The name of the file to read from and write to, and
- a word
- and make the program read the file, replace the word chocolate in it with the word the user picked, and save the resulting text back to the file.
- Verify that your program works correctly, and that it modifies the file you select and replaces chocolate with the word you choose.
Moodle Submission
Rename your program lab5_6.py, and submit your solution program for Challenge #5 to Moodle, in the Lab 5 PB 5 section.
Splitting Long Strings (Optional: Skip it if you do not have time)
In this section you will see how to take text represented as a multi-line string, and process it various ways.
- Long strings that span several lines can be created by enclosing them in triple quotes; either triple single-quotes (), or triple double-quotes (""").
- Copy/paste the program below in a new program. You may call it lab5.py
# lab5.py text = """Chocolate Chocolate is the first luxury. It has so many things wrapped up in it: Deliciousness in the moment, childhood memories, and that grin-inducing feeling of getting a reward for being good. --Mariska Hargitay""" def main(): # make sure main knows that this variable exists global text # split the long string into individual lines lines = text.split( "\n" ) # print each line for line in lines: print( line ) main()
- Run the program. Verify that it outputs the entirety of the text.
- Just to make sure we understand what the variable lines contain, make your program print lines, with a simple print( lines ) statement.
- Observe that it's just a regular Python list.
Challenge #7 |
- Modify your program, and make it print the poem so that each line is centered in a field of 60 spaces. You must use the text variable, and print its line. Do not create a new version of the poem!
- Expected output
Chocolate Chocolate is the first luxury. It has so many things wrapped up in it: Deliciousness in the moment, childhood memories, and that grin-inducing feeling of getting a reward for being good. --Mariska Hargitay
Challenge #8 |
- Make your program print the first line of the poem, centered, but also in uppercase.
- If you need to review the string methods, you may want to go to this page.
- Print a blank line after the title.
- Make it display the other lines centered, without changing their case.
- Print a blank line before the last line.
- Expected output
CHOCOLATE Chocolate is the first luxury. It has so many things wrapped up in it: Deliciousness in the moment, childhood memories, and that grin-inducing feeling of getting a reward for being good. --Mariska Hargitay
Challenge #9 |
- One more modification. Now make your program print the last line right-justified in a field of 60 spaces.
- The first line is still in upper-case.
- Make it display the other lines centered, without changing their case.
- If you need to review the string methods, you may want to go to this page.
- Expected output
CHOCOLATE Chocolate is the first luxury. It has so many things wrapped up in it: Deliciousness in the moment, childhood memories, and that grin-inducing feeling of getting a reward for being good. --Mariska Hargitay
Challenge #10 |
- Make your program print the poem in a box. The top and bottom lines have 50 dashes in them.
- Expected output
+--------------------------------------------------+ | CHOCOLATE | | | | Chocolate is the first luxury. | | It has so many things wrapped up in it: | | Deliciousness in the moment, | | childhood memories, | | and that grin-inducing | | feeling of getting a reward for being good. | | | | --Mariska Hargitay| +--------------------------------------------------+