Python 的“with"语句与“with .. as" [英] Python's 'with' statement versus 'with .. as'

问题描述

刚刚因为差异而脱掉头发，我想知道 Python 2.5 中真正有什么不同.

Having just pulled my hair off because of a difference, I'd like to know what the difference really is in Python 2.5.

我有两个代码块(dbao.getConnection() 返回一个 MySQLdb 连接).

I had two blocks of code (dbao.getConnection() returns a MySQLdb connection).

conn = dbao.getConnection()
with conn:
    # Do stuff

和

with dbao.getConnection() as conn:
    # Do stuff

我认为这些会产生相同的效果，但显然不是因为后一个版本的 conn 对象是 Cursor.游标从何而来，有没有办法以某种方式将变量初始化和 with 语句结合起来?

I thought these would have the same effect but apparently not as the conn object of the latter version was a Cursor. Where did the cursor come from and is there a way to combine the variable initialization and with statement somehow?

推荐答案

一般来说，由 with 语句的 as 部分分配的值将是上下文管理器的 __enter__ 方法返回的任何内容.

In general terms, the value assigned by the as part of a with statement is going to be whatever gets returned by the __enter__ method of the context manager.

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