w3resource

Python: Create a Caesar encryption

Python String: Exercise-25 with Solution

Write a Python program to create a Caesar encryption.

Note: In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. The method is named after Julius Caesar, who used it in his private correspondence.

Python String Exercises: Create a Caesar encryption

Sample Solution:-

Python Code:

#https://gist.github.com/nchitalov/2f2b03e5cf1e19da1525
def caesar_encrypt(realText, step):
	outText = []
	cryptText = []
	
	uppercase = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z']
	lowercase = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']

	for eachLetter in realText:
		if eachLetter in uppercase:
			index = uppercase.index(eachLetter)
			crypting = (index + step) % 26
			cryptText.append(crypting)
			newLetter = uppercase[crypting]
			outText.append(newLetter)
		elif eachLetter in lowercase:
			index = lowercase.index(eachLetter)
			crypting = (index + step) % 26
			cryptText.append(crypting)
			newLetter = lowercase[crypting]
			outText.append(newLetter)
	return outText

code = caesar_encrypt('abc', 2)
print()
print(code)
print()

Sample Output:

['c', 'd', 'e']

Flowchart:

Flowchart: Create a Caesar encryption

Visualize Python code execution:

The following tool visualize what the computer is doing step-by-step as it executes the said program:

Python Code Editor:

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous: Write a Python program to check whether a string starts with specified characters.
Next: Write a Python program to display formatted text (width=50) as output.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



Follow us on Facebook and Twitter for latest update.

Python: Tips of the Day

Sorting a list of lists:

Consider we have a list of lists:

lst = [[3, 5], [6, 8], [4, 6], [5, 8], [6, 7], [5, 8]]

We can sort the list based on the first or second items of the inner lists by using the sort function with a lambda function.

lst.sort(key = lambda inner:inner[1])
print(lst)

Output:

[[3, 5], [4, 6], [6, 7], [6, 8], [5, 8], [5, 8]]

The list is sorted based on the second items. We can do the same with the first items just by changing the 1 to 0.

lst.sort(key = lambda inner:inner[0])
print(lst)

Output:

[[3, 5], [4, 6], [5, 8], [5, 8], [6, 8], [6, 7]]