003_014 Python 简单加法器

代码如下：

#encoding=utf-8print '中国'#用Python实现加法器import decimal, re, operator  parse_input = re.compile(r'''(?x)           # 允许RE中的注释和空白符                      (\d+\.?\d*)             # 带有可选的小数部分的数                      \s*                     # 可选的空白符                      ([-+/*])                # 运算符                      $''')                   # 字符串结束  oper = { '+': operator.add, '-': operator.sub,                 '*': operator.mul, '/': operator.truediv,             }  total = decimal.Decimal('0')  def print_total( ):        print '=======  =\n', total        print """Welcome to Adding Machine:   Enter a number and operator,   an empty line to see the current subtotal,  or q to quit: """  while True:        try:              tape_line = raw_input( ).strip( )        except EOFError:              tape_line = 'q'       if not tape_line:              print_total( )              continue        elif tape_line == 'q':              print_total( )              break        try:              num_text, op = parse_input.match(tape_line).groups( )        except AttributeError:              print 'Invalid entry: %r' % tape_line              print 'Enter number and operator,empty line for total, q to quit'              continue        total = oper[op](total, decimal.Decimal(num_text)) 

感觉不能用，打印结果如下：

中国
Welcome to Adding Machine:   
Enter a number and operator,   
an empty line to see the current subtotal,  
or q to quit: 
1.2-2.3
Invalid entry: '1.2-2.3'
Enter number and operator,empty line for total, q to quit