003_014 Python 简单加法器

代码如下：

#encoding=utf-8

print '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