How can I split up a long f-string in Python? [duplicate]

Question

I am getting a line too long PEP 8 E501 issue.

f'Leave Request created successfully. Approvers sent the request for approval: {leave_approver_list}'

I tried using a multi-line string, but that brings in a \n, which breaks my test:

f'''Leave Request created successfully.
Approvers sent the request for approval: {leave_approver_list}'''

How can I keep it single line and pass PEP 8 linting?

This is indeed a partial duplicate, but the duplicate does not pertain to f strings, a slight modification is needed to that answer. — cs95
– cs95, Commented Feb 20, 2018 at 8:58
@cs95 I don't see why. All the same techniques work fundamentally the same way with f-strings. — Karl Knechtel
– Karl Knechtel, Commented May 24, 2024 at 2:44

tread · Accepted Answer · 2022-10-21 20:11:20Z

212

Use parentheses and string literal concatenation:

msg = (
    f'Leave Request created successfully. '
    f'Approvers sent the request for approval: {leave_approver_list}'
)

Note, the first literal doesn't need an f, but I include it for consistency/readability.

edited Oct 21, 2022 at 20:11

tread

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answered Feb 20, 2018 at 9:05

juanpa.arrivillaga

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9 Comments

moooeeeep Over a year ago

To add to that: "The preferred way of wrapping long lines is by using Python's implied line continuation inside parentheses, brackets and braces. Long lines can be broken over multiple lines by wrapping expressions in parentheses. These should be used in preference to using a backslash for line continuation."

Aidan H Over a year ago

The first line should not have an f

juanpa.arrivillaga Over a year ago

@AidanH why should it not? It makes no difference, so it comes down to a style choice. I prefer the f here so they line up. I can understand why people would feel otherwise, though. I actually noted this in the answer.

paxdiablo Over a year ago

Some tools will complain if you have an f-string with no actual interpolation (pylint or mypy does this, I think). You may need to tell the tool to not complain about that line.

juanpa.arrivillaga Over a year ago

@paxdiablo pylint does, but I don't hink mypy does

|

Peter Mortensen · Accepted Answer · 2022-04-27 12:46:47Z

21

You will need a line break unless you wrap your string within parentheses. In this case, f will need to be prepended to the second line:

'Leave Request created successfully.'\
f'Approvers sent the request for approval: {leave_approver_list}'

Here's a little demo:

In [97]: a = 123

In [98]: 'foo_'\
    ...: f'bar_{a}'
Out[98]: 'foo_bar_123'

I recommend juanpa's answer since it is cleaner, but this is one way to do this.

edited Apr 27, 2022 at 12:46

Peter Mortensen

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answered Feb 20, 2018 at 8:59

cs95

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3 Comments

Chris_Rands Over a year ago

"But f will need to be prepended to the second line"- why?

cs95 Over a year ago

@Chris_Rands Otherwise, the second line is treated as a literal string, and the variable is not substituted in.

cs95 Over a year ago

In your answer, you have a multiline string, so it is not required.

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