multiple conditions in conditional

So i'm not exactly sure how to ask this question exactly but basically I want to see if any value between two variables is also in between two other variables. So for instance here is a sample of what code might look like of what I'm explaining

var1 = 0
var2 = 20
var3 = 5
var4 = 15
if var3 <= [any variable between var1 and var2] <=var4:
    do something

so that's basically it, but I'm not sure what would go in place of the brackets or if there is another way to do it. Sorry if there's an easy solution, I'm pretty tired. Thanks!