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I'm using telnetlib.expect() to interface with a device that responds in bytestrings, apparently. Unless I use bytestrings in the regex passed to expect() (either precompiled, or literals), an exception is generated: TypeError: cannot use a string pattern on a bytes-like object. However, pycodestyle complains this is W605 invalid escape sequence '\d', and further reading makes me think this will become a Python syntax error in the future.

In summary:

telnetlib.expect([b'\d']) # OK, but W065
telnetlib.expect(['\d'] # TypeError
telnetlib.expect([r'\d'] # TypeError

Is there a way through this, or is pycodestyle simply wrong?

(BTW, can't seem to suppress the W065 in pycodestyle, other than suppressing all warnings.)

Quantum Mechanic
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1 Answers1

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Bytestring literals use \ as an escape character the same way string literals do. So similar to them you have to either use a raw bytestring literal rb'\d' or use double backslash b'\\d'.

From https://docs.python.org/3/reference/lexical_analysis.html#string-and-bytes-literals

In plain English: Both types of literals can be enclosed in matching single quotes (') or double quotes ("). They can also be enclosed in matching groups of three single or double quotes (these are generally referred to as triple-quoted strings). The backslash (\) character is used to escape characters that otherwise have a special meaning, such as newline, backslash itself, or the quote character.

Sebastian Proske
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