Python 3中打印单字节\xd0为何输出\xc3\x90？

Great question—this boils down to two core Python 3 behaviors that are easy to mix up: how string literals work, and how print() handles output encoding. Let's break it down step by step:

1. "\xd0" is a Unicode character, not a raw byte #

In Python 3, string literals ("" or '') represent Unicode strings, not sequences of raw bytes. When you write "\xd0", Python interprets the \x escape as a Unicode code point in the Latin-1 range (0x00 to 0xFF). Specifically, \xd0 maps to the Unicode character U+00D0 (LATIN CAPITAL LETTER ETH, Ð).

2. print() encodes Unicode strings to your system's default encoding #

The print() function doesn't write strings directly to stdout—it first encodes the Unicode string to a byte sequence using the default encoding of sys.stdout (almost always UTF-8 on modern systems).

The Unicode character U+00D0 has a UTF-8 encoding of c3 90—that's exactly the byte sequence you're seeing when you pipe to xxd.

How to output the raw byte \xd0 #

If you want to write the single byte 0xd0 to stdout (bypassing Unicode encoding), you need to work with a bytes object instead of a string, and write directly to the stdout buffer:

import sys
sys.stdout.buffer.write(b"\xd0")

Test this with your command line:

$ python -c 'import sys; sys.stdout.buffer.write(b"\xd0")' | xxd

You'll get the expected output:

00000000: d0

The b"\xd0" syntax creates a bytes object containing the raw byte 0xd0, and writing it to sys.stdout.buffer skips the Unicode encoding step that print() performs.

Quick Cheat Sheet #

• "\xd0": Unicode character U+00D0 (Ð) → encoded to UTF-8 as c3 90
• b"\xd0": Raw byte 0xd0 → written directly to stdout as d0

内容的提问来源于stack exchange，提问作者Aaron Esau