For a file name that begins with '~' or an environment varialbe, update the file name with the environment home directory.

update_file_home_path.py

#==========================================================================
## Simple method, just deal with the '~' notation for home
#==========================================================================
import os
FILE = "~/path/to/file.data"
FILE = FILE.replace('~', os.environ['HOME'])
#==========================================================================

#==========================================================================
## More involved, but deals with other environment variables
#==========================================================================
import os
FILE = "$HOME/$CENTER/path/to/file.data"
path = []
for i in FILE.split('/'):
    if i == '~':
        path.append(os.environ['HOME'])
    elif len(i) > 1 and i[0] == '$':
        path.append(os.environ[i[1:]])
    else:
        path.append(i)
FILE = '/'.join(path)
#==========================================================================