python将“ E”添加到串 [英] python adds "E" to string

问题描述

此字符串：

"CREATE USER %s PASSWORD %s", (user, pw)

总是扩展为：

CREATE USER E'someuser' PASSWORD E'somepassword'

有人可以告诉我为什么吗？

Can anyone tell me why?

编辑：
上面的扩展字符串是数据库在错误消息中给我的字符串。我正在使用psycopg2访问我的postgres数据库。实际代码如下：

The expanded string above is the string my database gives me back in the error message. I'm using psycopg2 to access my postgres database. The real code looks like this:

conn=psycopg2.connect(user=adminuser, password=adminpass, host=host)
cur = conn.cursor()

#user and pw are simple standard python strings the function gets as parameter
cur.execute("CREATE USER %s PASSWORD %s", (user, pw))
conn.commit()

推荐答案

不仅E，而且引号似乎来自user和pw的类型。 ％s只是做str（）的工作，这可能会退回到repr（），这两种方法都有相应的方法 __ str __ 和 __ repr __ 。另外，那不是生成结果的代码（我假设有一个％，但现在只看到一个逗号）。请使用实际的代码，类型和值来扩展您的问题。

Not only the E but the quotes appear to come from whatever type user and pw have. %s simply does what str() does, which may fall back to repr(), both of which have corresponding methods __str__ and __repr__. Also, that isn't the code that generates your result (I'd assumed there was a %, but now see only a comma). Please expand your question with actual code, types and values.

附录：考虑到它看起来像SQL，我冒昧地猜测您正在看到转义字符串常量，可能是由数据库接口模块或库正确生成的。

Addendum: Considering that it looks like SQL, I'd hazard a guess that you're seeing escape string constants, likely properly generated by your database interface module or library.

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