如何从字符串内部安全地获取字节文字

Question

As a challenge to myself, I wanted to see how I could safely extract a byte literal from inside a regular string. However, I'm not able to safely extract the byte literal out.

Example string:

'b"\\xfeq\\xed\\xad7E\'\\x9a\\xb4_ p\\xdf\\x98\\tC\\xcb\\xe7\\xaa\\x80`\\x93\\x1a\\xf5?\\x03j\\xa4\\x93vT\\xd9"'

Goal:

b"\xfeq\xed\xad7E'\x9a\xb4_ p\xdf\x98\tC\xcb\xe7\xaa\x80`\x93\x1a\xf5?\x03j\xa4\x93vT\xd9"

Answer 1

After spending some time going through the documentation, this was the best solution that I could come up with. ast.literal_eval Is the best way to evaluate literal expressions from untrusted sources. The except clause is left purposefully broad in order to accommodate for any possible errors.

import ast

def extract_binary_literal(input: str):
    try:
        result = ast.literal_eval(input)
        if type(result) == bytes:
            return result
    except Exception:
        pass
    return None