Python 3字节的奇怪表示法 [英] Strange notation for Python 3 bytes

问题描述

有人可以确定这些个字节的表示法是什么吗？乍一看，我倾向于认为是十六进制，但我不认识 xf1Y 和 e1fl 之类的东西是：

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'vy\xe9\xb5\xa2\xba\xf1Y\xe8\xe1fl\x1d\x87\xacC'

当我使用<$ c进行编码时，我会得到这个$ c> some_text.encode（'utf-8'）。

我正在尝试获取可传递给加密方法的字节，使用Python 2的字节字符串。

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

推荐答案

您是对的-这是一个十六进制表示法。

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

在字节文字中，不能由可打印的ASCII字符表示的任何字节（或标准转义符 \n ， \t 或 \r ）表示为 \xNN ，其中NN是字节的2位十六进制表示形式。

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

让您感到困惑的是，您误会了例如 \xf1Y 表示单个转义序列，实际上它表示两个单独的字节：

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']

如果迭代一个字节对象，您将获得字节的整数值：

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

>>> list(b'vy\xe9\xb5\xa2\xba\xf1Y\xe8\xe1fl\x1d\x87\xacC')
[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'

的文档href = https://docs.python.org/3.5/reference/lexical_analysis.html#index-18 rel = noreferrer> Python字符串和字节对象中的转义序列有关转义的更多信息Python可以理解的序列（尽管上面的序列是它用来表示字节对象的唯一序列）。

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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