Combining Python f-string and r-string not behaving as expected

Question

I have a variable that contains a string, that I'd like to print literally, so the newline is escaped. Printing the variable does not escape the newline:

bad_string = 'http://twitter.com/blo\r\n+omberg'
print(bad_string)
>>> http://twitter.com/blo
+omberg

Printing the value using an r-string results in what I'd want:

print(r'http://twitter.com/blo\r\n+omberg')
>>> http://twitter.com/blo\r\n+omberg

However, using an f-string with the variable, and combining it with an r-string, does not:

print(rf'{bad_string}')
>>> http://twitter.com/blo
+omberg

I'm confused why this happens. I'd expect the combination of r and f string to print it literally. How can I print the literal value of a string variable with an f-string?

I'm using Python 3.6.13

try something like this: ```bad_string = r'http://twitter.com/blo\r\n+omberg' ; print(f"{bad_string}")``` — tgpz, Feb 04 '22 at 16:06
thanks @tgpz, that works. However I'm loading pre-defined string variables - is there an easy way to convert the string variable to a raw string variable? — jammygrams, Feb 04 '22 at 16:10
thanks @Abhishek, that seems to output a b-string though - I'd still need to convert it to a plain string? — jammygrams, Feb 04 '22 at 16:14
Interestingly `print(f'{bad_string.encode().decode()}')` doesn't work, but `print(f'{bad_string.encode("unicode_escape").decode()}')` seems to — jammygrams, Feb 04 '22 at 16:17

score 2 · Accepted Answer · answered Feb 04 '22 at 16:11

Raw strings only concern themselves with the static literal part, so your rf'{bad_string}' is the same as bad_string.

Depending on what this is for, the repr builtin may be what you need

In [71]: print(repr("string\nwith\nnewline"))
'string\nwith\nnewline'

Or you can simply replace the newlines using the replace method.

There's also the unicode_escape "encoding", but this'll also replace any non ascii value:

In [77]: "\n".encode("unicode_escape").decode()
Out[77]: '\\n'

In [78]: "仮".encode("unicode_escape").decode()
Out[78]: '\\u4eee'

Combining Python f-string and r-string not behaving as expected

1 Answers1