How do you format a string when interpolated in Julia?

You can use @sprintf macro from the standard library package Printf. This returns a string rather than just printing it as @printf.

using Printf
x = 1.77715
print("I'm long: $x, but I'm alright: $(@sprintf("%.2f", x))")

Output:

I'm long: 1.77715, but I'm alright: 1.78