After this loop , stack contains unbalanced part of expression , i . e . , expression of the form " . . . . "
s = [ ] NEW_LINE for i in range ( lenn ) : NEW_LINE INDENT if ( expr [ i ] == ' ' and len ( s ) ) : NEW_LINE INDENT if ( s [ 0 ] == ' ' ) : NEW_LINE INDENT s . pop ( 0 ) NEW_LINE DEDENT else : NEW_LINE INDENT s . insert ( 0 , expr [ i ] ) NEW_LINE DEDENT DEDENT else : NEW_LINE INDENT s . insert ( 0 , expr [ i ] ) NEW_LINE DEDENT DEDENT