This is primarily for my recollection
To expand ~ in a path name:
os.path.expanduser('~')
To get the size of a directory:
import os
def getsize(start<em>path = '.'):
    totalsize = 0
    for dirpath, dirnames, filenames in os.walk(start</em>path):
        for f in filenames:
            fp = os.path.join(dirpath, f)
            totalsize += os.path.getsize(fp)
    return totalsize