Return the size of path in bytes if it exists and can be determined.

def get_size(path):
    '''Return the size of path in bytes if it exists and can be determined.'''
    size = os.path.getsize(path)
    for item in os.walk(path):
        for file in item[2]:
            size += os.path.getsize(os.path.join(item[0], file))
    return size