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How to Solve Caesar Cipher Helper in Python

The challenge

Write a class that, when given a string, will return an uppercase string with each letter shifted forward in the alphabet by however many spots the cipher was initialized to.

Example:

c = CaesarCipher(5); # creates a CipherHelper with a shift of five c.decode('BFKKQJX') # returns 'WAFFLES'
Code language: Python (python)

If something in the string is not in the alphabet (e.g. punctuation, spaces), simply leave it as is.
The shift will always be in the range of [1, 26].

The solution in Python code

Option 1:

from string import maketrans class CaesarCipher(object): def __init__(self, shift): self.alpha = "abcdefghijklmnopqrstuvwxyz".upper() self.newalpha = self.alpha[shift:] + self.alpha[:shift] def encode(self, str): t = maketrans(self.alpha, self.newalpha) return str.upper().translate(t) def decode(self, str): t = maketrans(self.newalpha, self.alpha) return str.upper().translate(t)
Code language: Python (python)

Option 2:

class CaesarCipher(object): def __init__(self, shift): self.s=shift pass; def encode(self, str): return ''.join(chr((ord(i)+self.s-ord('A'))%26+ord('A')) if i.isalpha() else i for i in str.upper()) def decode(self, str): return ''.join(chr((ord(i)-self.s+ord('A'))%26+ord('A')) if i.isalpha() else i for i in str.upper())
Code language: Python (python)

Option 3:

class CaesarCipher(object): def __init__(self, shift): abc = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' self.enc_dict = dict(zip(abc, abc[shift:] + abc[:shift])) self.dec_dict = dict(zip(abc[shift:] + abc[:shift], abc, )) def encode(self, str): return ''.join( self.enc_dict.get(c, c) for c in str.upper() ) def decode(self, str): return ''.join( self.dec_dict.get(c, c) for c in str.upper() )
Code language: Python (python)

Test cases to validate our solution

test.describe("Testing the CaesarCipher class"); test.it("Shift of 5"); c = CaesarCipher(5); test.assert_equals(c.encode('WAFFLES'), 'BFKKQJX'); test.assert_equals(c.decode('BFKKQJX'), 'WAFFLES'); test.assert_equals(c.encode("IT'S A SHIFT CIPHER!!"), "NY'X F XMNKY HNUMJW!!"); test.assert_equals(c.decode("NY'X F XMNKY HNUMJW!!"), "IT'S A SHIFT CIPHER!!"); test.it("Shift of 13"); c = CaesarCipher(13); test.assert_equals(c.encode('CNAPNXRF'), 'PANCAKES'); test.assert_equals(c.decode('PANCAKES'), 'CNAPNXRF'); test.assert_equals(c.encode('JAVASCRIPT'), 'WNINFPEVCG'); test.assert_equals(c.decode('WNINFPEVCG'), 'JAVASCRIPT'); from random import sample import string for i in range(, 5): rs = ''.join(sample(string.punctuation + string.ascii_uppercase, 10)); test.assert_equals(c.decode(c.encode(rs)), rs); test.it("Shift of 26"); c = CaesarCipher(26); for i in range(, 7): rs = ''.join(sample(string.punctuation + string.ascii_uppercase, 15)); test.assert_equals(c.decode(rs), rs); test.assert_equals(c.encode(rs), rs);
Code language: Python (python)

See also  Convert a LinkedList to a String in Python
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