(path)
return res
Expand shell variables of the forms $var, ${var} and %var%.

    Unknown variables are left unchanged.
Expand shell variables of the forms $var, ${var} and %var%.
Expand shell variables of the forms $var $ { var } and %var% .
def expandvars(path):
    """Expand shell variables of the forms $var, ${var} and %var%.

    Unknown variables are left unchanged."""
    if isinstance(path, bytes):
        if ord('$') not in path and ord('%') not in path:
            return path
        import string
        varchars = bytes(string.ascii_letters + string.digits + '_-', 'ascii')
        quote = b'\''
        percent = b'%'
        brace = b'{'
        dollar = b'$'
    else:
        if '$' not in path and '%' not in path:
            return path
        import string
        varchars = string.ascii_letters + string.digits + '_-'
        quote = '\''
        percent = '%'
        brace = '{'
        dollar = '$'
    res = path[:0]
    index = 0
    pathlen = len(path)
    while index < pathlen:
        c = path[index:index+1]
        if c == quote:   # no expansion within single quotes
            path = path[index + 1:]
            pathlen = len(path)
            try:
                index = path.index(c)
                res += c + path[:index + 1]
            except ValueError:
                res += path
                index = pathlen - 1
        elif c == percent:  # variable or '%'
            if path[index + 1:index + 2] == percent:
                res += c
                index += 1
            else:
                path = path[index+1:]
                pathlen = len(path)
                try:
                    index = path.index(percent)
                except ValueError:
                    res += percent + path
                    index = pathlen - 1
                else:
                    var = path[:index]
                    if isinstance(path, bytes):
                        var = var.decode('ascii')
                    if var in os.environ:
                        value = os.environ[var]
                    else:
                        value = '%' + var + '%'
                    if isinstance(path, bytes):
                        value = value.encode('ascii')
                    res += value
        elif c == dollar:  # variable or '$$'
            if path[index + 1:index + 2] == dollar:
                res += c
                index += 1
            elif path[index + 1:index + 2] == brace:
                path = path[index+2:]
                pathlen = len(path)
                try:
                    if isinstance(path, bytes):
                        index = path.index(b'}')
                    else:
                        index = path.index('}')
                    var = path[:index]
                    if isinstance(path, bytes):
                        var = var.decode('ascii')
                    if var in os.environ:
                        value = os.environ[var]
                    else:
                        value = '${' + var + '}'
                    if isinstance(path, bytes):
                        value = value.encode('ascii')
                    res += value
                except ValueError:
                    if isinstance(path, bytes):
                        res += b'${' + path
                    else:
                        res += '${' + path
                    index = pathlen - 1
            else:
                var = ''
                index += 1
                c = path[index:index + 1]
                while c and c in varchars:
                    if isinstance(path, bytes):
                        var += c.decode('ascii')
                    else:
                        var += c
                    index += 1
                    c = path[index:index + 1]
                if var in os.environ:
                    value = os.environ[var]
                else:
                    value = '$' + var
                if isinstance(path, bytes):
                    value = value.encode('ascii')
                res += value
                if c:
                    index -= 1
        else:
            res += c
        index += 1
    return res
def expandvars ( path ) : if isinstance ( path , bytes ) : if ord ( '$' ) not in path and ord ( '%' ) not in path : return path import string varchars = bytes ( string . ascii_letters + string . digits + '_-' , 'ascii' ) quote = b'\'' percent = b'%' brace = b'{' dollar = b'$' else : if '$' not in path and '%' not in path : return path import string varchars = string . ascii_letters + string . digits + '_-' quote = '\'' percent = '%' brace = '{' dollar = '$' res = path [ : 0 ] index = 0 pathlen = len ( path ) while index < pathlen : c = path [ index : index + 1 ] if c == quote : # no expansion within single quotes path = path [ index + 1 : ] pathlen = len ( path ) try : index = path . index ( c ) res += c + path [ : index + 1 ] except ValueError : res += path index = pathlen - 1 elif c == percent : # variable or '%' if path [ index + 1 : index + 2 ] == percent : res += c index += 1 else : path = path [ index + 1 : ] pathlen = len ( path ) try : index = path . index ( percent ) except ValueError : res += percent + path index = pathlen - 1 else : var = path [ : index ] if isinstance ( path , bytes ) : var = var . decode ( 'ascii' ) if var in os . environ : value = os . environ [ var ] else : value = '%' + var + '%' if isinstance ( path , bytes ) : value = value . encode ( 'ascii' ) res += value elif c == dollar : # variable or '$$' if path [ index + 1 : index + 2 ] == dollar : res += c index += 1 elif path [ index + 1 : index + 2 ] == brace : path = path [ index + 2 : ] pathlen = len ( path ) try : if isinstance ( path , bytes ) : index = path . index ( b'}' ) else : index = path . index ( '}' ) var = path [ : index ] if isinstance ( path , bytes ) : var = var . decode ( 'ascii' ) if var in os . environ : value = os . environ [ var ] else : value = '${' + var + '}' if isinstance ( path , bytes ) : value = value . encode ( 'ascii' ) res += value except ValueError : if isinstance ( path , bytes ) : res += b'${' + path else : res += '${' + path index = pathlen - 1 else : var = '' index += 1 c = path [ index : index + 1 ] while c and c in varchars : if isinstance ( path , bytes ) : var += c . decode ( 'ascii' ) else : var += c index += 1 c = path [ index : index + 1 ] if var in os . environ : value = os . environ [ var ] else : value = '$' + var if isinstance ( path , bytes ) : value = value . encode ( 'ascii' ) res += value if c : index -= 1 else : res += c index += 1 return res