This is a modified version of the xkcd scream cipher https://xkcd.com/3054

screamcipher.py

"xkcd scream cipher implementation"
import string

As = ['\u0041', '\u00c0', '\u00c1', '\u00c2', '\u00c3', '\u00c4', '\u00c5', '\u0100', '\u0102', '\u0104', '\u01cd', '\u01de', '\u01e0', '\u01fa', '\u0200', '\u0202',
    '\u0226', '\u023a', '\u1e00', '\u1ea0', '\u1ea2', '\u1ea4', '\u1ea6', '\u1ea8', '\u1eaa', '\u1eac', '\u1eae', '\u1eb0', '\u1eb2', '\u1eb4', '\u1eb6'
]
letters = [c for c in ',.()-'] + [c for c in string.ascii_lowercase]

def encrypt(s: str) -> str:
    r = ''
    for c in s.lower():
        if c in letters:
            r += As[letters.index(c)]
        else:
            r += c
    return r

def decrypt(s: str) -> str:
    r = ''
    for c in s:
        if c in As:
            r += letters[As.index(c)]
        else:
            r += c
    return r

if __name__ == '__main__':
    # command line usage...
    import sys
    
    if '-h' in sys.argv or '--help' in sys.argv:
        print("""XKCD Scream Cipher encryptor/decryptor
usage: {0} [encrypt|decrypt]""".format(sys.argv[0]))
    
    if len(sys.argv) == 1:
        i = input('Encrypt or decrypt: ').lower()
        j = input('Input: ')
    elif len(sys.argv) <= 2:
        i = sys.argv[1]
        if len(sys.argv) <= 3:
            j = ' '.join(sys.argv[2:])
        else:
            j = input('Input: ')
    if i == 'encrypt':
        print(encrypt(j))
    elif i == 'decrypt':
        print(decrypt(j))
    else:
        print(repr(i), 'is not either \'encrypt\' or \'decrypt\'.')

And it is now tested: all of string.printable both encrypts and decrypts successfully. Only issue is that the program decrypts everything lowercase…