posixpath.py 文件源码

def expanduser(path):
    """Expand ~ and ~user constructions.  If user or $HOME is unknown,
    do nothing."""
    if isinstance(path, bytes):
        tilde = b'~'
    else:
        tilde = '~'
    if not path.startswith(tilde):
        return path
    sep = _get_sep(path)
    i = path.find(sep, 1)
    if i < 0:
        i = len(path)
    if i == 1:
        if 'HOME' not in os.environ:
            import pwd
            userhome = pwd.getpwuid(os.getuid()).pw_dir
        else:
            userhome = os.environ['HOME']
    else:
        import pwd
        name = path[1:i]
        if isinstance(name, bytes):
            name = str(name, 'ASCII')
        try:
            pwent = pwd.getpwnam(name)
        except KeyError:
            return path
        userhome = pwent.pw_dir
    if isinstance(path, bytes):
        userhome = os.fsencode(userhome)
        root = b'/'
    else:
        root = '/'
    userhome = userhome.rstrip(root) or userhome
    return userhome + path[i:]


# Expand paths containing shell variable substitutions.
# This expands the forms $variable and ${variable} only.
# Non-existent variables are left unchanged.