New submission from Glenn Linderman : I noticed the following description for f-strings:

Escape sequences are decoded like in ordinary string literals (except when a literal is also marked as a raw string). After decoding, the grammar for the contents of the string is:

followed by lots of stuff, followed by

Backslashes are not allowed in format expressions and will raise an error: f"newline: {ord('\n')}" # raises SyntaxError

If f-strings are processed AS DESCRIBED, the \n would never seen by the format expression... but in fact, it does produce an error. PEP 498 has a more accurate description, that the {} parsing actually happens before the escape processing. The string or raw-string escape processing is done only to the literal string pieces. So the string content is first parsed for format expressions enclosed in {}, on the way, converting {{ and }} to { and } in the literal parts of the string, and then the literal parts are treated exactly like independent string literals (with regular or raw-string escaping performed), to be concatenated with the evaluation of the format expressions, and subsequent literal parts. The evaluation of the format expressions presently precludes the use of # and \ for comments and escapes, but otherwise tries to sort of by the same as a python expression possibly followed by a format mini-language part. I am not the expert here, just the messenger. ---------- assignee: docs@python components: Documentation messages: 349370 nosy: docs@python, v+python priority: normal severity: normal status: open title: f-string documentation not fully accurate versions: Python 3.6, Python 3.7, Python 3.8, Python 3.9 _______________________________________ Python tracker https://bugs.python.org/issue37816 _______________________________________