辅导Engineering 265、讲解Python程序设计、辅导via Gitlab、讲解Python

Software Engineering 265

Software Development Methods

Fall 2018

Assignment 3

Due: Sunday, November 25th, 11:55 pm by submission via Gitlab

Due: Sunday, December 2nd, 11:55 pm by submission via Gitlab

(no late submissions accepted)

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.

Individual work

This assignment is to be completed by each individual student (i.e., no group work).

Naturally you will want to discuss aspects of the problem with fellow students, and

such discussion is encouraged. However, sharing of code fragments is strictly

forbidden without the express written permission of the course instructor. If

you are still unsure regarding what is permitted or have other questions about what

constitutes appropriate collaboration, please contact me as soon as possible. (Code—

similarity analysis tools may be used to examine submitted programs.)

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.

Page 2 of 5

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.

Page 3 of 5

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"

]

Page 4 of 5

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"

]

Page 5 of 5

% ./sengfmt2.py /home/seng265/assign3/in11.txt > ./myout11.txt

% cat ~/seng265/assign3/in11.txt | ./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. 1

The program is clearly written and uses functions appropriately

(i.e., is well structured).

1

Errors have been enumerated and are either suitably handled or a

sensible response strategy has been suggested.

2

Program can handle both stdin and file inputs. 2

Code passes the first set of test cases for multiple “?mrgn” (1 to 3) 3

Code passes the second set of test cases for “?maxwidth” (4 to 6) 3

Code passes the second set of test cases for “?replace” (7 to 8) 4

Code passes the third set of test cases for “?monthabbr”(9 to 10) 4

Total 20