The text of the addition is fine. But I am wondering whether such a subtle point should be part of theintroduction.rst. Perhaps keep only the first line and refer to a location with details?

(not sure what would be a better location)

It's not strictly a part of this file, seehttps://docs.python.org/3/reference/lexical_analysis.html:

... even a raw string cannot end in an odd number of backslashes ...

The text you added in this PR will end up here:https://docs.python.org/3/tutorial/introduction.html#strings right?

It is an informal introduction, so I would write something like:

There is one subtle aspect to raw strings: a raw string may not end in an odd
number of\ characters. For details seeString and Bytes literals

But the text added is correct, so it is mostly a matter of style.

Re-reading this, I realize that my comment above doesn't actually address your original concern on whether this is too subtle of a point for the tutorial introduction - IMO, since the section above does talk about escaping quotes as well as raw strings, I think it's somewhat natural to at least mention the case with them combined.

As for how brief a mention, the current phrasing can definitely be made more brief. I think also that just one of the workarounds can be left in, while the other two examples put elsewhere, along with the wording specific to Windows paths. If the section would introduce the problem of raw strings not ending in an odd number of slashes, I think it should also suggest some sort of solution to it, so I would prefer keeping one example in.

As for moving the rest of the information, I don't think the reference is the most appropriate place, maybe instead in some FAQ entry or a howto page?

An FAQ entry sounds reasonable. Maybe we do something likeThere is one subtle aspect to raw strings: a raw string may not end in an odd number of \ characters; see [the FAQ entry] for workarounds?

Maybe to be explicit, it could be something like

Thanks for making the change! This looks good, but let's move it to the FAQ section?

My reasoning is based on the description of raw strings it's not really surprising that the backslash is preserved. It's only really surprising in the context of the end quote situation, where the backslash "escapes" the quote for the tokeniser, but not for the actual value.

That is, if you read:

A raw string ending with an odd number of backslashes will escape the string's quote

you may come away with the impression that raw strings are raw except for quotes or something. I guess a concrete phrasing would be adding the following to the end of the FAQ entry:

Note that while a backslash will "escape" a quote for the purposesof determining where the raw string ends, there are no escapesequences that affect the interpretation of the value of the raw string.That is, the backslash remains present in the value of the raw string::>>> r'backslash\'preserved'"backslash\\'preserved"

Okay, there's prior art. Here's the relevant words fromLexical Analysis:

Even in a raw literal, quotes can be escaped with a backslash, but the backslash remains in the result; for example,r"\"" is a valid string literal consisting of two characters: a backslash and a double quote;r"\" is not a valid string literal (even a raw string cannot end in an odd number of backslashes). Specifically, a raw literal cannot end in a single backslash (since the backslash would escape the following quote character). Note also that a single backslash followed by a newline is interpreted as those two characters as part of the literal, not as a line continuation.

Hmm, I'm not too certain what the tokenization / determining where the raw string ends means too well, but I've commited the changes (and added a link to the reference) for the time being.