Python's os.makedirs doesn't understand "~" in my path

You need to expand the tilde manually:

my_dir = os.path.expanduser('~/some_dir')

The conversion of ~/some_dir to $HOME/some_dir is called tilde expansion and is a common user interface feature. The file system does not know anything about it.

In Python, this feature is implemented by os.path.expanduser:

my_dir = os.path.expanduser("~/some_dir")

That's probably because Python is not Bash and doesn't follow same conventions. You may use this:

homedir = os.path.expanduser('~')