Python Caesar Cipher

while(True):
 message = input("What would you like the message to say? ").lower()
 newmessage = ""
 for i in range(0,26):
    for letter in message:
        decimal = (ord(letter))
        decimal = decimal + i

        if decimal > 122:
            decimal = decimal -26

        elif decimal < 97:
            decimal = decimal + 26

        newmessage += (chr(decimal))

    print (newmessage)
    newmessage = ""

• Use functions to do the rotation – If you have learned about functions I would strongly suggest to use functions to do the actual rotation. You call it with the string to rotate and rotation offset, and you'll get the rotated string in return.

• Avoid magic numbers – In your code you use magic numbers like 122 and 97, your code looks cleaner if you replace these by what they actually are: ord('z') and ord('a'). Alternatively use constants like ALPHABET_LENGTH = 26, but I'll come back to this one

• Don't hide reserved words or modules – decimal is a module in Python, and to use that as a variable name is considered bad practice.

• Naming scheme dictates to use snake_case –  Instead of newmessage it is recommended to use new_message and similar. This reads more easy.

• Be consistent on indentation – You use a varying amount of spaces to indent your code, please be consistent and use 4 spaces. The previous and this item is related to conforming to the PEP8 guidelines. Please read and follow these guidelines, as that is quite common when using Python.

• What about letters not in the lowercase alphabet? – You don't handle punctuation chracters and non-alpha characters so these would leave somewhat strange behaviour

• You don't have a means to exit your code – You are essential having an eternal loop, leaving you to kill the program execution as only means of leaving it

• Range checks can be joined in Python – Instead of doing one lower than and one larger than you could do 97

• range() default to start at 0 – That is range(0, 26) and range(26) is the same, and the latter is preferred for clarity

• You don't need to do (expr), unless you want line continuation – It is better to write new_message += chr(decimal) without the extra parentheses. You could use them if you want to spread the expression within over multiple lines, but normally keep the expression without.

ALPHABET_LENGTH = 26

while(True):
    message = input("What would you like the message to say? ").lower()

    if message == "quit":
        break

    for i in range(ALPHABET_LENGTH):
        new_message = ""
        for letter in message:
            if 'a' <= letter <= 'z':
                char_pos = ord(letter) - ord('a')

                # Rotate by i, and make sure we're within alphabet
                char_pos = (char_pos + i) % ALPHABET_LENGTH

                new_message += chr(char_pos + ord('a'))

                # new_message += chr((ord(letter) - ord('a') + i) % ALPHABET_LENGTH + ord('a'))
            else:
                new_message += letter

        print (new_message)

from string import ascii_lowercase

def rotate_lowercase_char(char, offset):
    """Return lowercase  rotated by  characters.

    If  is a lowercase character rotate it, or else return
    it unchanged allowing for non-alpha characters to be present."""

    if not char in ascii_lowercase:
        return char
    else:
        position = ascii_lowercase.index(char)
        position = (position + offset) % len(ascii_lowercase)
        return ascii_lowercase[position]

def rotate_lowercase_text(text, offset):
    """Return  rotated by  characters."""

    return ''.join(rotate_lowercase_char(letter, offset) for letter in text)

def main():

    while(True):
        message = input("What would you like the message to say? ").lower()

        if message == "quit":
            break

        for i in range(len(ascii_lowercase)):
            print("Offset: {}, Rotated: {}".format(i, rotate_lowercase_text(message, i)))

if __name__ == '__main__':
    main()