Coursework 2

Data Structures and Iteration

Python Task

Your task is to develop a program that encodes/decodes Morse Code.

Task Overview:

Morse code is a character encoding scheme used in telecommunications. It is named after the inventor of the telegraph Samuel Morse and represents textual characters as combinations of long (dashes) and short (dots) electronic pulses, lights or sounds.

For example, the letter J is coded as .---, ! as -.-.-- and 1 as .−−−−

A single space is used to separate characters within a word and 3 spaces between words. Morse is case-insensitive, so capital letters are used as a matter of course.

For example, the message HELLO WORLD in Morse code is:

.... . .-.. .-.. ---  .-- --- .-. .-.. -..

In addition to letters, digits and punctuation, there are some special service codes, the most notorious   of   which   is   the   international   distress   signal SOS,   coded   as ...−−−... These special codes are treated as single characters, but transmitted as separate words. You can experiment with the conversion of text to Morse code and back on many websites online, e.g. https://morsedecoder.com/

Getting Started:

Start by downloading the file morse_code.py from Canvas. Add your name and student number to the top of the file. Read the included documentation.

Program Requirements:

You will develop a program capable of encoding and decoding Morse code. In order to do this, you will be required to implement several functions, specified in the template provided.

Once complete, your programs main() method should do the following:

1.   Prompt users to select a mode (encode or decode).

2.   Check if the mode the user entered is valid. If not, continue to prompt the user until a valid mode is selected.

3.   Prompt the user for the message they would like to encode/decode.

4.   Encode/decode the message as appropriate and print the output.

5.   Prompt the user whether they would like to encode/decode another message.

6.   Check if the user has entered a valid input (y/n) If not, continue to prompt the user until they enter a valid response. Depending upon the response you should either:

a.   End the program if the user selects no.

b.   Proceed directly to step 2 if the user says yes.

General Hints:

•    You can make use of str.split() to generate a list of Morse words and characters by using the spaces between words and characters as a separator.

>>> morse = '.... . .-.. .-.. ---   .-- --- .-. .-.. -..'

>>> words = morse.split('   ') # 3 spaces used to separate words

>>> words # List containing 2 words in Morse

['.... . .-.. .-.. ---', '.-- --- .-. .-.. -..']

>>> for word in words:

...     characters = word.split(' ') # 1 space between letters

...     characters

...

['....', '.', '.-..', '.-..', '---'] ['.--', '---', '.-.', '.-..', '-..']

•    You will also find str.join() useful for constructing a string from a list of strings.

>>> characters

['.--', '---', '.-.', '.-..', '-..', '-.-.--']

>>> ' '.join(characters)

'.-- --- .-. .-.. -.. -.-.--'

•    You should use a loop to keep the programming running if the user says that would like to encode/decode more messages.

•    Your  program  should  handle  both  uppercase  and  lowercase  inputs.  You  can  use

str.upper() and str.lower() to convert strings to a specific case.

Example Implementation (user input in red):

Welcome to Wolmorse

This program encodes and decodes Morse code. Would you like to encode (e) or decode (d): g Invalid Mode

Would you like to encode (e) or decode (d): d

What message would you like to decode: .... . .-.. .-.. ---                                              .-

- --- .-. .-.. -.. HELLO WORLD

Would you like to encode/decode another message? (y/n): t

Would you like to encode/decode another message? (y/n): y

Would you like to encode (e) or decode (d): e

What message would you like to encode: Hello WORld

.... . .-.. .-.. ---   .-- --- .-. .-.. -..

Would you like to encode/decode another message? (y/n): n

Thanks for using the program, goodbye!

Structure and Documentation

The structure of your code and documentation will be analyzed and assessed.

This will be done using a static analysis tool called Pylint. This software checks the code in your program, ensures that it follows Python conventions and that all functions, classes and modules have been documented. You can read more about it here:  https://www.pylint.org/.

Python has an official style guide named PEP8, which is where most Python conventions/coding standards originate from. Example checks that Pylint carries out to ensure that the PEP8 coding standard is followed include things such as:

•    checking line-code's length

•    checking if variable names are well-formed (snake case)

•    checking if imported modules/functions are used

•    checking if variables/function parameters are used

It is a good idea to run these checks on your code at regular intervals and before submitting. There are several free websites that allow you to do this e.g. http://pep8online.com/

Note: Marks will be deducted for warning and errors detected in your code.

Implementation Details

Step 1 – Implementing the print_intro Function:

To implement this function, you simply need to print an introduction to the user. You should use the following message:

Welcome to Wolmorse

This program encodes and decodes Morse code.

Step 2 – Implementing the get_input Function:

To implement this function, you need to request input from the user to determine the mode of conversion and the message that they would like to encode/decode.

Your function should check if the mode the user entered is valid. If not, it should continue to prompt the user until a valid mode is selected.

The function should return two strings, the mode of conversation and the message. The message should be converted to upper case to avoid potential encoding/decoding issues.

Example Implementation:

>>> get_input()

Would you like to encode (e) or decode (d): g

Invalid Mode

Would you like to encode (e) or decode (d): e

What message would you like to encode: Hello WORld

('e', 'HELLO WORLD')

Step 3 – Implementing the encode Function:

To implement this function, you need to correctly encode a plain text message as Morse Code. It should take a single parameter, the message to be encoded.

You should use the MORSE_CODE tuple to convert between plain text/Morse code

Your function should return a single value, a string - the encoded Morse.

Example Implementation:

>>> encode("Hello World")

".... . .-.. .-.. ---   .-- --- .-. .-.. -.."

Step 4 – Implementing the decode Function:

To implement this function, you need to correctly decode a message in Morse Code. It should take a single parameter, the message to be decoded.

You should use the MORSE_CODE tuple to convert between plain text/Morse code

Your function should return a single value, a plain text string.

Example Implementation:

>>> decode(".... . .-.. .-.. ---   .-- --- .-. .-.. -..") "HELLO WORLD"

Task 2 Python

Introduction:

The Morse Code encoder/decoder that you’ve developed works well, however, one major drawback is that it’s only capable of encoding/decoding a single message at a time. Therefore, your task for this challenge will be to attempt to resolve this issue by implementing file reading/writing capabilities so that multiple messages can be encoded/decoded in one go.

To do this, you will need to implement the process_lines(),                                 write_lines(), check_file_exists and  get_filename_input() functions.

The first function process_lines() should take two parameters, the filename from which messages should be read and the mode of operation (encoding/decoding). It should process the lines in the file one by one, returning a list of encoded/decoded messages.

A file has been added to the assessment page on Canvas, morse_input.txt, that includes a series of plain text strings, which you can use to test your function.

Example Implementation:

>>> process_lines("morse_input.txt", "e")

['.... . .-.. .-.. ---', '.... . .-.. .-.. ---  .-- --- .-.

.-.. -..', '.-- .... .- - -.-.-- ..--..', '...  ---  ...',

'-----   .----   ..---  ...--  ....-  .....  -....  --...

---..   ----.', '- .... .  --.- ..- .. -.-. -.-  -... .-. --

- .-- -.   ..-. --- -..-  .--- ..- -- .--. ...  --- ...- .

.-.   - .... .   .-.. .- --.. -.--  -.. --- --. .-.-.-']

The second function check_file_exists() should take a single parameter, a filename and return a Boolean value (True/False) depending upon whether the file exists within the current folder. There are several ways that you can achieve this, for example using exception handling logic or through the built-in OS module included with Python.

Example Implementation:

>>> check_file_exists("morse_input.txt") True

The third function write_lines() should take a single parameter, a list of strings. It should write these strings to a file called results.txt, with each item taking up a single line.

The function doesn’t need to return anything.

The  fourth  function  get_filename_input() should  work  similarly  to  the get_input() function you developed earlier. It shouldn’t take any parameters, but needs to return three values, the mode ("e" or "d" based on whether the user would like to encode/decode), a message if the user would like to process messages using the console (or None) and a filename if the user would like to process data in a file (or None). You should continue to validate the mode that the user enters as well as the input mechanism (file/console).

In addition, you should call your check_file_exists() function to verify filenames. Users should be repeatedly prompted to enter the filename if the file doesn’t exist.

Example Implementation:

>>> get_filename_input()

Would you like to encode (e) or decode (d): g

Invalid Mode

Would you like to encode (e) or decode (d): e

Would you like to read from a file (f) or the console (c)? f

Enter a filename: something_silly.txt

Invalid Filename

Enter a filename: morse_input.txt

('e', None, morse_input.txt)

>>> get_filename_input()

Would you like to encode (e) or decode (d): g

Invalid Mode

Would you like to encode (e) or decode (d): e

Would you like to read from a file (f) or the console (c)? c

What message would you like to encode: Hello WORld

('e', 'HELLO WORLD', None)

You will also need to update your main() function to call the functions you’ve implemented.

Full Example Implementation (user input in red)

Welcome to Wolmorse

This program encodes and decodes Morse code. Would you like to encode (e) or decode (d): g Invalid Mode

Would you like to encode (e) or decode (d): d

Would you like to read from a file (f) or the console (c)? c

What message would you like to decode: .... . .-.. .-.. ---                                              .-

- --- .-. .-.. -..

HELLO WORLD

Would you like to encode/decode another message? (y/n): y

Would you like to encode (e) or decode (d): e

Would you like to read from a file (f) or the console (c)? c

What message would you like to encode: Hello WORld

.... . .-.. .-.. ---   .-- --- .-. .-.. -..

Would you like to encode/decode another message? (y/n): y

Would you like to encode (e) or decode (d): e

Would you like to read from a file (f) or the console (c)? f

Enter a filename: something_silly.txt

Invalid Filename

Enter a filename: morse_input.txt

Output written to results.txt

Would you like to encode/decode another message? (y/n): n

Thanks for using the program, goodbye!