Description
need help with the following python problem. Would really appreciate it if you attach an algorithm for the program in a separate text file.
Sample Run:
Here’s a sample run of the basic program in action.
SECRET DECODER MENU
0) Quit
1) Encode
2) Decode
What is your choice: 1
text to be encoded: Python Rocks!
AQULEWKEMNJ
SECRET DECODER MENU
0) Quit
1) Encode
2) Decode
What is your choice: 2
code to be decyphered: AQULEWKEMNJ
PYTHONROCKS
SECRET DECODER MENU
0) Quit
1) Encode
2) Decode
What is your choice: 0
Thanks for doing secret spy stuff with me.
Starter Code
You may copy and paste the following code into your editor to get started. You may also type the code by hand, but your main method must be identical to the one posted here:
“”” crypto.py
Implements a simple substitution cypher
“””
alpha = “ABCDEFGHIJKLMNOPQRSTUVWXYZ”
key = “XPMGTDHLYONZBWEARKJUFSCIQV”
def main():
keepGoing = True
while keepGoing:
response = menu()
if response == “1”:
plain = input(“text to be encoded: “)
print(encode(plain))
elif response == “2”:
coded = input(“code to be decyphered: “)
print (decode(coded))
elif response == “0”:
print (“Thanks for doing secret spy stuff with me.”)
keepGoing = False
else:
print (“I don’t know what you want to do…”)
#my starter code.
if __name__ == “__main__”:
main()
Notes
Please keep the following ideas in mind:
This is a substitution cypher
Each letter is replaced by another letter with no repetition
Ignore spaces and punctuation
You must account for spaces (I ignored them, but there are other legitimate responses.)
The best program will also account for punctuation and other symbols. (Ignoring them is fine.) Your program can ignore these special characters when they occur, but it should not crash if it encounters a strange character.
Manage Capitalization
In most cryptographic applications, all letters are converted to uppercase. Please follow this convention or deal with potential case conversion problems in another way.
Use Functions
You may not make significant changes to the main function. Determine which functions are necessary and create them. (The blackbelt project does allow for one slight modification, noted below.) Do not turn in a program with only a main() function!! Write the code necessary for Python to run the main function as expected
Pass data between functions
Your functions may require some input and return some output. Part of the task is to determine how the methods are to be created.
Using a key
There’s several workable answers, but I used a string with all the alphabet characters and a second string with a “scrambled” version of the alphabet.
Useful String methods
This program is all about string manipulation, so you may want to use help(“str”) in your python shell to look up some useful techniques. Here are a few things you might need to know how to do:
determine the length of a string
convert a string to upper case
find the position of a character in a string
Determine the character at a certain position in a string
Don’t send spy messages with this
The encryption used here is laughably weak. This is an interesting exercise in cryptography, but it’s nowhere near useable as an encryption tool. Don’t encode your secret recipe with this thing and expect it to remain secret.
Test your program
The best way to test your program is to encrypt a phrase, and then decrypt the encoded phrase to see if you got the original (sans spaces and other punctuation.)
Use standard code only
Python is an exceptionally high-level language and includes a number of libraries for simplifying encryption including a cool function called “maketrans” and a number of specific cryptographic libraries. You are welcome to experiment with any of these techniques for the black-belt extension, but your main program should stay within the core Python language. There should be no need to import any libraries for your basic version. Python does have a String.translate() method, but please do not use it for the basic assignment. Remember, the goal is not to create a crypto program, but to experiment with building your own translater to learn string manipulation and functions.
Note that array manipulation is not necessary for this project. All work can be done directly with strings. You may need some exception-handling, though.
