python之检查用户输入的长度

我正在尝试检查用户输入的字符串的长度，如果它小于 5，它就会通过，但是无论它的长度如何，它仍然会通过我的 try except 语句

打印“”” 请填写公司股票代号 您希望看到其最后收盘价。"""

while True: 
   symbol = raw_input("Enter Stock Symbol: ") 
   try: 
      len(symbol) < 5 
      break 
 
   except ValueError: 
      print 'Greater than 4 characters, Try again' 
 
print 'Great your stock symbol is less than 5' 

请您参考如下方法:

你不需要尝试/异常(exception):

while True: 
   symbol = raw_input("Enter Stock Symbol: ") 
   if len(symbol) > 4:        
      print 'Greater than 4 characters, Try again' 
   else: 
       print 'Great your stock symbol {} is less than 5'.format(symbol) 
       break 
 
 
In [3]: paste 
while True: 
   symbol = raw_input("Enter Stock Symbol: ") 
   if len(symbol) > 4:        
      print 'Greater than 4 characters, Try again' 
   else: 
       print 'Great your stock symbol {} is less than 5'.format(symbol) 
       break 
 
## -- End pasted text -- 
Enter Stock Symbol: FOOBAR 
Greater than 4 characters, Try again 
Enter Stock Symbol: YHOO 
Great your stock symbol YHOO is less than 5 

在您的代码中:

try: 
    len(symbol) < 5 # always checks len 
    break # always breaks 
except ValueError: 

例如，如果您想将输入强制转换为 int 并在那里捕获 ValueError，则可以使用 try/except，但它不适用于您的情况。