store operator and numbers in different vectors
for i in range ( len ( exp ) ) : NEW_LINE INDENT if ( isOperator ( exp [ i ] ) ) : NEW_LINE INDENT opr . append ( exp [ i ] ) NEW_LINE num . append ( int ( tmp ) ) NEW_LINE tmp = " " NEW_LINE DEDENT else : NEW_LINE INDENT tmp += exp [ i ] NEW_LINE DEDENT DEDENT