下面的re.findall（）代码有什么错误？

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：
4
＆LT;＆LT;＆LT;
＆LT;＆GT;＆LT;
＆LT; =＆GT;
＆LT; =＆LT;
如果我运行上面的代码，我遇到一个错误。我在SO上读它只是语法仍然是我收到错误：

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。

Python＆gt; = 3.4

max采用可选的默认参数：

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

Python＆lt; 3.4

添加警卫以检查列表是否为空

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