ROT Caesar Cipher | Python Fiddle

"""
Name: ROT13

Purpose: Encode/decode text strings using the ROT13 Caesar cipher

Features:
- Encodes//descoes text strings using the ROT13 Caesar cipher
- Preserves punctuation, digits, and whitespace

Examples:
print ROT13('Hello!') --> 'Uryyb!'

print ROT13('Hello there!') --> 'Uryyb gurer!'

print ROT13('I am 10 years old') --> 'V nz 10 lrnef byq'

print ROT13("How can you tell an extrovert from an introvert at NSA? Va gur ryringbef, gur rkgebireg ybbxf ng gur BGURE thl'f fubrf.")

-->'Ubj pna lbh gryy na rkgebireg sebz na vagebireg ng AFN? In the elevators, the extrovert looks at the OTHER guy's shoes.'

print ROT13(ROT13('Hello there!')) --> 'Hello there!'

See more at: http://pythonfiddle.com/rot-caesar-cipher#sthash.hs1VEB6w.dpuf
"""

inList = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'

outList = 'NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm'

converstionDict = dict(zip(inList,outList))

def ROT13 (s):
    outList = []
    outString = ''
    
    for letter in s:
        if letter in inList:
            outList.append(converstionDict[letter])
        else:
            outList.append(letter)
    
    outString = outString.join(outList)
    
    return outString

print ROT13('Hello!')

print ROT13('Hello there!')

print ROT13('I am 10 years old')

print ROT13("How can you tell an extrovert from an introvert at NSA? Va gur ryringbef, gur rkgebireg ybbxf ng gur BGURE thl'f fubrf.")

print ROT13(ROT13('Hello there!'))

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