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GH-109190: Copyedit 3.12 What's New: PEP 701 (#109655)

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Adam Turner 2023-09-21 20:37:28 +01:00 committed by GitHub
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@ -153,12 +153,13 @@ New Features
PEP 701: Syntactic formalization of f-strings
---------------------------------------------
:pep:`701` lifts some restrictions on the usage of f-strings. Expression components
inside f-strings can now be any valid Python expression including backslashes,
unicode escaped sequences, multi-line expressions, comments and strings reusing the
same quote as the containing f-string. Let's cover these in detail:
:pep:`701` lifts some restrictions on the usage of :term:`f-strings <f-string>`.
Expression components inside f-strings can now be any valid Python expression,
including strings reusing the same quote as the containing f-string,
multi-line expressions, comments, backslashes, and unicode escape sequences.
Let's cover these in detail:
* Quote reuse: in Python 3.11, reusing the same quotes as the containing f-string
* Quote reuse: in Python 3.11, reusing the same quotes as the enclosing f-string
raises a :exc:`SyntaxError`, forcing the user to either use other available
quotes (like using double quotes or triple quotes if the f-string uses single
quotes). In Python 3.12, you can now do things like this:
@ -181,11 +182,12 @@ same quote as the containing f-string. Let's cover these in detail:
>>> f"{f"{f"{f"{f"{f"{1+1}"}"}"}"}"}"
'2'
* Multi-line expressions and comments: In Python 3.11, f-strings expressions
must be defined in a single line even if outside f-strings expressions could
span multiple lines (like literal lists being defined over multiple lines),
making them harder to read. In Python 3.12 you can now define expressions
spanning multiple lines and include comments on them:
* Multi-line expressions and comments: In Python 3.11, f-string expressions
must be defined in a single line, even if the expression within the f-string
could normally span multiple lines
(like literal lists being defined over multiple lines),
making them harder to read. In Python 3.12 you can now define f-strings
spanning multiple lines, and add inline comments:
>>> f"This is the playlist: {", ".join([
... 'Take me back to Eden', # My, my, those eyes like fire
@ -195,10 +197,10 @@ same quote as the containing f-string. Let's cover these in detail:
'This is the playlist: Take me back to Eden, Alkaline, Ascensionism'
* Backslashes and unicode characters: before Python 3.12 f-string expressions
couldn't contain any ``\`` character. This also affected unicode escaped
sequences (such as ``\N{snowman}``) as these contain the ``\N`` part that
previously could not be part of expression components of f-strings. Now, you
can define expressions like this:
couldn't contain any ``\`` character. This also affected unicode :ref:`escape
sequences <escape-sequences>` (such as ``\N{snowman}``) as these contain
the ``\N`` part that previously could not be part of expression components of
f-strings. Now, you can define expressions like this:
>>> print(f"This is the playlist: {"\n".join(songs)}")
This is the playlist: Take me back to Eden
@ -210,7 +212,7 @@ same quote as the containing f-string. Let's cover these in detail:
See :pep:`701` for more details.
As a positive side-effect of how this feature has been implemented (by parsing f-strings
with the PEG parser (see :pep:`617`), now error messages for f-strings are more precise
with :pep:`the PEG parser <617>`, now error messages for f-strings are more precise
and include the exact location of the error. For example, in Python 3.11, the following
f-string raises a :exc:`SyntaxError`: