Real Python: Python News: What's New From January 2023

The new year has arrived, and January brought a flurry of new and interesting Python enhancement proposals (PEPs). Topics range from f-string formalization and no-GIL Python to packaging. There’s been ample discussion on the Python Discourse forum about the implications of these PEPs, and if you’re still a bit wary of diving deeper into the discussions, then you can get a softer introduction here.

There have also been a couple of noteworthy new releases, first and foremost the fourth alpha release of Python 3.12. And finally, there’s a new job posting out for a security developer in residence sponsored by the Python Software Foundation (PSF).

Let’s dive into the biggest Python news from the past month!

PEP 701 Attempts to Formalize f-Strings

Python’s f-strings are great, but there are currently a few edge cases that might make you scratch your head.

For example, maybe you wanted to greet the new year with a carefully constructed f-string, but you ran into unexpected troubles:

>>> f"happy {"\n".join(["twenty","three","🥳"])#it's 2023!}!!"File "<stdin>", line 1  f"happy {"\n".join(["twenty", "three", "🥳"]) # it's 2023!}!!"             ^SyntaxError: unexpected character after line continuation character

You used some double quotes (") inside the curly braces ({}). It looks like Python isn’t happy with that and considers the f-string closed, even though the quotes appear inside the f-string expression part.

The new year is still fresh, so you won’t let this get you down! You just change the double quotes to single quotes:

>>> f"Happy {'\n'.join(['twenty','three','🥳'])#Yes!2023!}!!"File "<stdin>", line 1  f"Happy {'\n'.join(['twenty', 'three', '🥳']) # Yes! 2023!}!!"                                                               ^SyntaxError: f-string expression part cannot include a backslash

Oh! There’s another issue with your new year’s greeting f-string. It looks like you can’t include the backslash (\) character in an f-string expression. Well, maybe 2023 is more about expanding in breadth than in depth, you think to yourself. So you replace the newline character (\n) with a whitespace character (' ') and try again:

>>> f"Happy {' '.join(['twenty','three','🥳'])#Yes!2023!}!!"File "<stdin>", line 1  f"Happy {' '.join(['twenty', 'three', '🥳']) # Yes! 2023!}!!"                                                              ^SyntaxError: f-string expression part cannot include '#'

Argh! Yet another problem! It seems like you can’t include comments in the f-string expression part—not even when they’re full of joy and optimism!

Python 3.6 introduced f-strings, and the LL(1) parser that Python used back then wasn’t able to handle these edge cases.

Maybe running into the limitations of f-strings has slightly dampened your optimistic beginning of 2023. But don’t write this year off quite yet, because these limitations may go away soon.

Pablo Galindo Salgado authored PEP 701 – Syntactic formalization of f-strings at the end of last year. The PEP proposes a formalized grammar for f-strings, which could be directly integrated into the parsing expression grammar (PEG) parser that Python’s been using since version 3.9.