Question

import re 
for test in range(int(input())): 
    a = input()     # input a string 
    n = a.replace("=", "")  # if string contains '='then remove it 
    gg = re.findall(r ">+", n) # count > 
    l1 = len(max(gg, key = len)) # count consecutive > 
    hh = re.findall(r "<+", n) # count < 
    l2 = len(max(hh, key = len)) # count consecutive < 
    print(max(l1, l2) + 1)  # print max of two + 1 

输入是：
< < <
< > <
< =>
< = <
我遇到错误，如果我运行上述code.I上阅读SO只有语法仍然我得到错误：

Traceback (most recent call last):<br/> File "/home/fea0d5e04ac92cb3a1e4f041940f2dfc.py", line 8, in <module><br/> 
l2=len(max(hh, key=len))<br/> ValueError: max() arg is an empty sequence 

Answer 1

max在空序列上失败。

的Python> = 3.4

max有一个可选的默认参数：

l1 = len(max(gg, key = len, default=0)) # count consecutive >

的Python < 3.4

添加保护检查列表是空的

if len(hh) > 0: 
    l2 = len(max(hh, key = len)) # count consecutive < 
else: 
    l2 = 0