An f-string will not work if the f prefix is missing.

Literal String Interpolation aka f-strings (because of the leading character preceding the string literal) were introduced by PEP 498. Prefix a string with the letter "f" and it’s now an f-string:

name = "jeff"
print(f"My name is {name}")

String interpolation is meant to be simpler with f-strings. However our research show 10% of repositories have one of these f-string mistakes:

Missing prefix:

bad

good

-

"hello {name}"

+

f"hello {name}"

Prefix was written inside the string:

bad

good

-

"fhello {name}"

+

f"hello {name}"

Concatenated strings uses the prefix on only the first string.

bad

good

-

f"hello {name}" + "do you like {food}?"

+

f"hello {name}" + f"do you like {food}?"