Multiline expression brackets with format specifiers don't work in f-strings

[tusharsadhwani]

Bug report

Bug description:

In accordance with PEP 701, the following code works:

>>> x = 1
>>> f"___{
...     x
... }___"
'___1___'

>>> f"___{(
...     x
... )}___"
'___1___'

But the following fails:

f"__{
    x:d
}__"

This gives:

  File "<stdin>", line 1
    x:d
SyntaxError: unterminated f-string literal (detected at line 2)

Is this intended behaviour? This is not clarified in the PEP.

---

Similarly,

f"""__{
    x:d
}__"""

Gives:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: Invalid format specifier 'd
' for object of type 'int'

CPython versions tested on:

3.12

Operating systems tested on:

macOS

Linked PRs

• gh-110259: Fix f-strings with multiline expressions and format specs #110271
• [3.12] gh-110259: Fix f-strings with multiline expressions and format specs (GH-110271) #110396

[pablogsal]

Thanks for the report! I have opened #110271 to fix it

[ericvsmith]

I'd be careful on that last one. If x is a datetime.datetime, it's a valid format spec.

>>> x=datetime.datetime.now()
>>> f"""__{
...    x:d
... }__"""
'__d\n__'

[ericvsmith]

In case that's not clear: format specs for datetime.datetime can contain any characters, and are passed on to strftime. Perhaps more usefully:

>>> f"""__{
...     x:%Y
... %m
... %d
... }__"""
'__2023\n10\n03\n__'