ord()：字元轉成ASCII碼，引數為字元。
chr()：ASCII碼轉成字元，引數為數字（0-127）

>>> help(ord)    # ord的幫助文件
Help on built-in function ord in module builtins:
ord(c, /)
    Return the Unicode code point for a one-character string.

>>> help(chr)    # chr的幫助文件
Help on built-in function chr in module builtins:
chr(i, /)
    Return
 
 a Unicode string of one character with ordinal i; 0 <= i <= 0x10ffff.

>>> ord('a')    # 例子
97
>>> chr(97)
'a'