ASCII is a 7-bit character-encoding standard with 128 values, including English letters, digits, punctuation, and control characters. Only 95 values are printable. It remains a common lowest denominator for data exchange, but it cannot represent most writing systems or many accented characters. section 21.2.1
Python exposes ASCII characters through ordinary strings and numeric escape sequences:
- Octal escapes use a backslash followed by three octal digits, such as '\155'. section 6.3.2
- Hexadecimal escapes begin with '\x' and continue through hexadecimal digits, such as '\x6D'. section 6.3.2
- Both forms can represent nonprintable ASCII characters, such as newline: '\012' or '\x0A'. section 6.3.2
ASCII bytes versus broader text
A file containing bytes [65, 66, 67, 255, 192, 193] may display as 'ABCÿÀÁ' under one interpretation. Reading it as UTF-8 raises UnicodeDecodeError because bytes outside the ASCII range do not identify their encoding by themselves. UTF-8 preserves basic ASCII while supporting a much larger character set. section 21.2.1
'm' 'm' '\155' 'm' '\x6D' 'm'
Compare three spellings of the same ASCII character: a literal, an octal escape, and a hexadecimal escape. section 6.3.2
