"Integer" means "whole number".
1 is an integer,
1.4 is not.
Second, you're not using a string at all.
var new_str = 1.4
creates a float variable with a value of
var new_str = "1.4"
would create a string.
If all you want is
1.4 then you already have that.
If you do have a string such as
"1.4" and you want to convert to a float, then you should use
float() instead of