以后会陆续补充
偶然在Python Cookbook看到一个format操作，想到一个问题, 感觉用了!r之后，会把传入的对象按照原来形式保留
d = {"foo": "bar"}
"value in d is {!r}".format(d["bar"])
想到一个用处，举个例子:
params = ("woody", "suxiaoji", "zy")
sql = "select userId from user where username in {!r}".format(params)
print(sql)
