Python 3 字节的奇怪符号 [英] Strange notation for Python 3 bytes

问题描述

有人可以识别这些 bytes 的符号是什么吗?乍一看，我倾向于认为十六进制"，但我不认识xf1Y 和e1fl 之类的东西是什么:

b'vyxe9xb5xa2xbaxf1Yxe8xe1flx1dx87xacC'

我在使用 some_text.encode('utf-8') 编码时得到这个.

我正在尝试获取可以传递给使用 Python 2 字节字符串的加密方法的字节.

解决方案

你说得对——它是一种十六进制表示法.

在字节文字中，任何不能用可打印的 ASCII 字符(或标准转义符 、 或 之一)表示的字节> ) 表示为 xNN，其中 NN 是字节的 2 位十六进制表示.

让您感到困惑的是，您弄错了，例如xf1Y 用于单个转义序列，实际上它代表两个单独的字节:

<预><代码>>>>len(b'xf1Y')2>>>[bytes([b]) for b in b'xf1Y'][b'xf1', b'Y']

如果你遍历一个字节对象，你会得到字节的整数值:

<预><代码>>>>列表(b'vyxe9xb5xa2xbaxf1Yxe8xe1flx1dx87xacC')[118, 121, 233, 181, 162, 186, 241, 89, 232, 225, 102, 108, 29, 135, 172, 67]>>>字节([118])b'v'>>>字节([121])经过'>>>字节([233])b'xe9'

Python 字符串和字节对象中的转义序列的文档 有更多关于 Python 理解的转义序列的信息(尽管以上是它用来表示字节对象的唯一信息).

Can someone identify what this notation for these bytes is? At first glance, I tend to think "hexadecimal", but I don't recognize what things like xf1Y and e1fl are:

b'vyxe9xb5xa2xbaxf1Yxe8xe1flx1dx87xacC'

I get this when I encode things using some_text.encode('utf-8').

I am trying to get bytes that I can pass to cryptography methods that worked with Python 2's byte strings.

解决方案

You're right – it's a hexadecimal notation.

In a bytes literal, any byte which can't be represented by a printable ASCII character (or one of the standard escapes , or ) is represented as xNN, where NN is the 2-digit hexadecimal representation of the byte.

What's confusing you is that you're mistaking e.g. xf1Y for a single escape sequence, when in fact it represents two separate bytes:

>>> len(b'xf1Y')
2
>>> [bytes([b]) for b in b'xf1Y']
[b'xf1', b'Y']

If you iterate over a bytes object, you'll get the integer values of the bytes back:

>>> list(b'vyxe9xb5xa2xbaxf1Yxe8xe1flx1dx87xacC')
[118, 121, 233, 181, 162, 186, 241, 89, 232, 225, 102, 108, 29, 135, 172, 67]
>>> bytes([118])
b'v'
>>> bytes([121])
b'y'
>>> bytes([233])
b'xe9'

The documentation for escape sequences in Python string and bytes objects has a little more information on escape sequences Python understands (although those above are the only ones it uses to represent bytes objects).

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