1、%，代表数学运算符号，求模；
2、%还用在python的格式化输出，比如：
a = ‘test’
print ‘it is a %s’ %(a)
打印的结果就是 it is a test
3、PYTHON中数据库操作
https://blog.csdn.net/qq_30008595/article/details/84995241?ops_request_misc=&request_id=&biz_id=102&utm_term=python%20%E8%AF%BB%E5%8F%96%E5%86%99%E5%85%A5%E6%95%B0%E6%8D%AE%E5%BA%93&utm_medium=distribute.pc_search_result.none-task-blog-2allsobaiduweb~default-9-84995241.first_rank_v2_pc_rank_v29&spm=1018.2226.3001.4187
