大家好，我的代码是掉入坑里了？为什么每次循环5次都是相同的UA，我想五次获取不同的UA，该如何写?
user_agent 是一个ua的列表，从setting导入

from setting import user_agent
import random



reload(sys)
sys.setdefaultencoding('utf8')

def ua():
    return random.choice(user_agent)


header = {
    "Accept":"text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8",
    "Accept-Encoding":"gzip, deflate, br",
    "Accept-Language":"zh-CN,zh;q=0.9",
    "Connection":"keep-alive",
    "Upgrade-Insecure-Requests":"1",
    "User-Agent":ua()
}

for url in range(5):
    print header

代码执行结果：

{'Accept-Language': 'zh-CN,zh;q=0.9', 'Accept-Encoding': 'gzip, deflate, br', 'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8', 'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3) AppleWebKit/535.20 (KHTML, like Gecko) Chrome/19.0.1036.7 Safari/535.20', 'Connection': 'keep-alive', 'Upgrade-Insecure-Requests': '1'}
{'Accept-Language': 'zh-CN,zh;q=0.9', 'Accept-Encoding': 'gzip, deflate, br', 'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8', 'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3) AppleWebKit/535.20 (KHTML, like Gecko) Chrome/19.0.1036.7 Safari/535.20', 'Connection': 'keep-alive', 'Upgrade-Insecure-Requests': '1'}
{'Accept-Language': 'zh-CN,zh;q=0.9', 'Accept-Encoding': 'gzip, deflate, br', 'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8', 'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3) AppleWebKit/535.20 (KHTML, like Gecko) Chrome/19.0.1036.7 Safari/535.20', 'Connection': 'keep-alive', 'Upgrade-Insecure-Requests': '1'}
{'Accept-Language': 'zh-CN,zh;q=0.9', 'Accept-Encoding': 'gzip, deflate, br', 'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8', 'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3) AppleWebKit/535.20 (KHTML, like Gecko) Chrome/19.0.1036.7 Safari/535.20', 'Connection': 'keep-alive', 'Upgrade-Insecure-Requests': '1'}
{'Accept-Language': 'zh-CN,zh;q=0.9', 'Accept-Encoding': 'gzip, deflate, br', 'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8', 'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3) AppleWebKit/535.20 (KHTML, like Gecko) Chrome/19.0.1036.7 Safari/535.20', 'Connection': 'keep-alive', 'Upgrade-Insecure-Requests': '1'}

都是相同的ua，如何改，能改为不同的UA呢？在函数里