Function with text replacement

I trying to write a "code generator" so I have to replace the letters with symbols. But every time I tried to run the code I got the answer none. How can I fix that? Here is the code:
codeOrDecode = input ("Wanna code a text or decode? [For decode write d, and for code write c] ")

if codeOrDecode == "c":
    textcode = input("What text wanna code? Paste it here: ")
    def howToCode (texttobereplaced) :
        codedText = textcode.replace(" " , "•")
        codedText = textcode.replace("a" , "✡")
        codedText = textcode.replace("A" , "✡")
        codedText = textcode.replace("b" , "➛")
        codedText = textcode.replace("B" , "➛")
        codedText = textcode.replace("c" , "▹")
        codedText = textcode.replace("C" , "▹")
        codedText = textcode.replace("d" , "◷")
        codedText = textcode.replace("D" , "◷")
        codedText = textcode.replace("e" , "▇")
        codedText = textcode.replace("E" , "▇")
        codedText = textcode.replace("f" , "Φ")
        codedText = textcode.replace("F" , "Φ")
        codedText = textcode.replace("g" , "≣")
        codedText = textcode.replace("G" , "≣")
        codedText = textcode.replace("h" , "➽")
        codedText = textcode.replace("H" , "➽")
        codedText = textcode.replace("i" , "◦")
        codedText = textcode.replace("I" , "◦")
        codedText = textcode.replace("j" , "○")
        codedText = textcode.replace("J" , "○")
        codedText = textcode.replace("k" , "❃")
        codedText = textcode.replace("K" , "❃")
        codedText = textcode.replace("l" , "◛")
        codedText = textcode.replace("L" , "◛")
        codedText = textcode.replace("m" , "▲")
        codedText = textcode.replace("M" , "▲")
        codedText = textcode.replace("n" , "‡")
        codedText = textcode.replace("N" , "‡")
        codedText = textcode.replace("o" , "▎")
        codedText = textcode.replace("O" , "▎")
        codedText = textcode.replace("p" , "◉")
        codedText = textcode.replace("P" , "◉")
        codedText = textcode.replace("q" , "⚂")
        codedText = textcode.replace("Q" , "⚂")
        codedText = textcode.replace("r" , "Δ")
        codedText = textcode.replace("R" , "Δ")
        codedText = textcode.replace("s" , "⋮")
        codedText = textcode.replace("S" , "⋮")
        codedText = textcode.replace("t" , "⅛")
        codedText = textcode.replace("T" , "⅛")
        codedText = textcode.replace("u" , "▯")
        codedText = textcode.replace("U" , "▯")
        codedText = textcode.replace("v" , "▧")
        codedText = textcode.replace("V" , "▧")
        codedText = textcode.replace("w" , "⠓")
        codedText = textcode.replace("W" , "⠓")
        codedText = textcode.replace("x" , "↬")
        codedText = textcode.replace("X" , "↬")
        codedText = textcode.replace("y" , "↜")
        codedText = textcode.replace("Y" , "↜")
        codedText = textcode.replace("z" , "⠽")
        codedText = textcode.replace("Z" , "⠽")
    print (howToCode(textcode))

How to fix that? I tried every thing I know.

The issue you had was due to the fact that your howToCode() function didn't explicitly return anything. Therefore, it implicitly returned None.

Also worth mentioning that you could do this using str.maketrans and str.translate leading to much less code.

Here's an example:

a = ' ABCDEFGHIJKLMNOPQRSTUVWXYZ'
b = '•✡➛▹◷▇Φ≣➽◦○❃◛▲‡▎◉⚂Δ⋮⅛▯▧⠓↬↜⠽'

ENCODE = str.maketrans(a, b)
DECODE = str.maketrans(b, a)

def howToCode(text: str, encode: bool = True) -> str:
    return text.upper().translate(ENCODE if encode else DECODE)

text = input('What text wanna code? Paste it here: ')

encoded = howToCode(text)
print(encoded)
decoded = howToCode(encoded, False)
print(decoded)

Console:

What text wanna code? Paste it here: hello world
➽▇◛◛▎•⠓▎Δ◛◷
HELLO WORLD