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.

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:

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Python: Tips of the Day
Check if a given key already exists in a dictionary:
In is the intended way to test for the existence of a key in a dict.
d = {"key1": 10, "key2": 23} if "key1" in d: print("this will execute") if "nonexistent key" in d: print("this will not")
If you wanted a default, you can always use dict.get():
d = dict() for i in range(100): key = i % 10 d[key] = d.get(key, 0) + 1
and if you wanted to always ensure a default value for any key you can either use dict.setdefault() repeatedly or defaultdict from the collections module, like so:
from collections import defaultdict d = defaultdict(int) for i in range(100): d[i % 10] += 1
but in general, the in keyword is the best way to do it.
Ref: https://bit.ly/2XPMRyz
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