Assignment 3 Advanced text formatter

Software Engineering 265
Software Development Methods

Assignment 3

Programming environment
For this assignment you must ensure your work executes correctly on the Linux
machines in ELW B238 (i.e., these have Python 3 installed). You are free to do some
of your programming on your own computers; if you do this, give yourself a few
days before the due date to iron out any bugs in the Python script you have
uploaded to the lab machines.

Objectives of this assignment
 Continue to learn features of the Python 3 language. (To enable this in your
environment when logged into the lab, type in the following command at the
start of your session at the shell prompt: setSENG265
 Use some of the object—oriented features of Python 3.
 Use some of the error—handling features of Python 3.
 Use some of the regular—expression functionality in Python 3.
 Use Gitlab to manage changes in your source code and annotate the
evolution of your solution with “messages” provided during commits.
 Test your code against the ten provided test cases.
 Be prepared to justify your script’s handling of errors for this assignment. 
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This assignment: “sengfmt2.py” & “formatter.py” for object–oriented features
For this assignment you will be wrapping a solution to the formatting problem
into a class. The class constructor will be given either a filename or a list as a
parameter. The formatted output will be available from the class instance via the
“get_lines()” method.
 The class must be named “Formatter” and appear in a file named
“formatter.py” which contains most of the methods you previously
developed in “sengfmt.py”.
 The script that uses this class will be in a new file named “sengfmt2.py”.
(similar to driver.py but can handle fileinput, rather than a static long
string).
o If a non–blank filename is provided to the sengfmt2.py script, then
that file will be opened and its contents formatted.
o If no name is provided to the sengfmt2.py script, then the contents of
stdin will be formatted.
 If the formatter.py object is used without being called from sengfmt2.py, and
no filename is provided to the constructor (i.e., None is passed as filename
argument), then the lines in the list provided as a parameter will be
formatted. Put differently, the Formatter constructor will accept (besides
“self”) a string and a list as parameters. Have a look at the code in
driver.py in the a3_files directory to find out how a list is passed to the
constructor in sengfmt2.py. (driver.py must therefore work with your
code!)
 The formatting specifications from the second assignment are, for the most
part, to be used for this assignment. However, there are two small changes:
two “?mrgn” commands may appear right after each other in an input file;
and a file may have more than one “?maxwidth” command.
Here are the two new commands you need to implement in this assignment:
 ?replace pattern1 pattern2: Each line following the command will be
formatted such that any matched sub-strings with the first argument
pattern1 will be replaced by the second argument pattern2. You need to
use the “re” module in Python 3 and complete the replacement before
applying any other formats. You can consider both pattern1 and
pattern2 can be generalized to formal regular expressions and they are
separated by a single white space.
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Example1:
Example2:
Input:
[
 "?maxwidth 24",
 "?mrgn 4",
 "?replace acknowledgment know",
 "What must acknowledgment shall be"
]
Output:
[
 " What must know",
 " shall be"
]
Input:
[
 "?maxwidth 24",
 "?mrgn 4",
 "?replace What You",
 "What must acknowledgment shall be"
]
Output:
[
 " You must",
 " acknowledgment ",
 " shall be"
]
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 ?monthabbr [off/on]: Each line following the command will be
formatted such that any recognizable date in the format of
“mm/dd/yyyy” or “mm-dd-yyyy” or “mm.dd.yyyy” (not a regular
expression, you need to create one) will be replaced with the new date
format “MMM. dd, yyyy” in which “MMM” stands for the month
abbreviation. You can import and use the calendar module to convert
the month number to month abbreviation. You can only focus on the
above three variants and ignore other date formats like “yyyy-mm-dd”.
You can show your concerns in the error handling file.
import calendar
month_number = 1
print(calendar.month_abbr[month_number])
‘Jan’
Example3:
 Note that if “?fmt” command is turned off, then all the formatting will NOT
apply.
You must now provide some error handling.
 Your task is to enumerate the things that could go wrong when faced with
such a formatting task in a plain text file named “error_handling.txt”, and to
either provide or suggest the code for handling each error item.
 The solution must be written in Python 3 and work correctly on the
workstations in the ELW B238 laboratory.
Input:
[
 "?maxwidth 24",
 "?mrgn 4",
 "?monthabbr on",
 "I dropped the course on 12/07/2018"
]
Output:
[
 " I dropped the course",
 " on Dec. 07, 2018"
]
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% python3 ./sengfmt2.py /home/seng265/assign3/in11.txt ./myout11.txt
% cat ~/seng265/assign3/in11.txt | python3 ./sengfmt2.py ./myout11.txt
With your completed “sengfmt2.py” script, the input would be transformed into the
output (here redirected to a file) via one of the two following UNIX commands:
where the file “myout11.txt” would be placed in your current directory.
Exercises for this assignment
1. Within your Gitlab project create an “A3” subdirectory. Use the test files in
a3_files.zip. (Files in01.txt through to in20.txt are based on those from the
second assignment, but letters with diacritics have been transliterated into
two separate characters.) Your “sengfmt2.py” and “formatter.py” script files
must appear here. Ensure the subdirectory and files are added to Gitlab
version control.
2. Reasonable run—time performance of your script is expected. None of the test
cases should take longer than 15 seconds to complete on a machine in ELW
B238.
What you must submit
 Python 3 files named “sengfmt2.py” and “formatter.py” within your
subversion repository (i.e., containing a solution to Assignment #3).
 A text file named “error_handling.txt” which enumerates the errors that are
addressed by your submission.
Evaluation
Our grading scheme is relatively simple.
Requirement Marks
File “sengfmt2.py” and “formatter.py” runs without errors. 2
The program is clearly written and uses functions appropriately
(i.e., is well structured).
3
Errors have been enumerated and are either suitably handled or a
sensible response strategy has been suggested.
3
Program can handle both stdin and file inputs. 2
Code passes the first set of test cases for multiple “?mrgn” (1 to 3) Bonus
+1
Code passes the second set of test cases for multiple “?maxwidth”
(4 to 6)
Bonus
+1
Code passes the third set of test cases for “?replace” (7) 5
Code passes the second set of test cases for “?replace” combined
with “?mrgn” and “?maxwidth” (8)
Bonus
+1
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Code passes the third set of test cases for “?monthabbr”(9) 5
Code passes the second set of test cases for “?monthabbr”
combined with “?mrgn” and “?maxwidth” (10)
Bonus
+1
Total 20
+ (4)