os.makedirs doesn’t understand “~” in my path

I have a little problem with ~ in my paths.

This code example creates some directories called ~/some_dir and do not understand that I wanted to create some_dir in my home directory.

my_dir = "~/some_dir"
if not os.path.exists(my_dir):
    os.makedirs(my_dir)

Note this is on a Linux-based system.