🔒 How to properly combine F strings and raw strings with () and regex?

[signal blaze]

what I am trying to achieve:

country = "United States (USA)"
out = rf"<title>{country} ([\d\.]*.?)</title>"

I want the above to give me
out = rf"<title>United States \(USA\) ([\d\.]*.?)</title>"
but it does not escape the parentheses.

When I try

country = "United States \(USA\)"
out = rf"<title>{country} ([\d\.]*.?)</title>"

I instead get
out = rf"<title>United States \\(USA\\) ([\d\.]*.?)</title>"

[lyric depot]

@signal blaze

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[soft valve]

Do you mean that the value of out is "<title>United States \\(USA\\) ([\d\.]*.?)</title>"? (I'm not including the r and f modifiers here, the distinction is important)

!e

country = "United States \(USA\)"
out = rf"<title>{country} ([\d\.]*.?)</title>"
print(out)

[lyric depot]

:white_check_mark: Your 3.12 eval job has completed with return code 0.

001 | /home/main.py:1: SyntaxWarning: invalid escape sequence '\('
002 |   country = "United States \(USA\)"
003 | <title>United States \(USA\) ([\d\.]*.?)</title>

[soft valve]

Ignore the warning, the print is the third line

As you can see there's only one slash

That's because in \\ The first slash is used to escape the second one

So overall you get one slash

[quasi hare]

You want:

out = rf".....(re.escape(country)}...."

re.escape is from the re module, and escapes a string so that it can be used in a regepx to match that string.

... and it sounds like you might be confusing the escaped nature of the rendering of the string from its actual contents.

How are you displaying the resulting value in out?

[soft valve]

If you don't want the warning then put an r for the country variable as well

[meager wing]

raw strings are not necessarily built for Regex - they do not "know" what regex escape patterns are, and they will not automatically escape those characters when you use string formatting

If you use newline = '\n'; string = rf'hello {newline} world' it will include a newline character, and if you use newline = r'\n'; string = rf'hello {newline} world' it will include \ and n

[soft valve]

But yes, re.escape is a good option

[quasi hare]

It's the correct option, if you're trying to embed an arbitrary literal string inside a regexp.

[soft valve]

if you don't know what the string contains then yeah

[signal blaze]

ah I’ll just use re.escape

I am providing all the strings but I’d rather not edit all of them to have backslashes

[quasi hare]

Both tedious and error prone.

Always better to provide the strings in the pure form, and let a computer mangle them to go inside a regexp 🙂 Computers don't get bored.

[lyric depot]

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