第一种：

    def get_ua(self):
        first_num = random.randint(55, 62)
        third_num = random.randint(0, 3200)
        fourth_num = random.randint(0, 140)
        os_type = [
            '(Windows NT 6.1; WOW64)', '(Windows NT 10.0; WOW64)', '(X11; Linux x86_64)',
            '(Macintosh; Intel Mac OS X 10_12_6)'
        ]
        chrome_version = 'Chrome/{}.0.{}.{}'.format(first_num, third_num, fourth_num)
        ua = ' '.join(['Mozilla/5.0', random.choice(os_type), 'AppleWebKit/537.36',
                       '(KHTML, like Gecko)', chrome_version, 'Safari/537.36']
                      )
        return ua

第二种：

pip install fake-useragent

from fake_useragent import UserAgent
ua=UserAgent()
print(ua.random)