tl;dr We found that 10% of the 666 most popular Python open source GitHub repositories had the following f-string typo bugs: f prefix was missing:"hello {name}"instead of f"hello {name}" .f prefix was written inside the string: "fhello {name}"instead of f"hello {name}" . We even saw an example of "hello f{name}" .Concatenated strings used the f prefix on only the first string: f"hello {name}" + "d