blocks|key|1336313|text|我认为你应该这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1336314|from+__future__+import+with_statement

with+open("out.txt","wt")+as+file_out:
++++with+open("in.txt")+as+file_in:
++++++++for+line+in+file_in:
++++++++++++file_out.write(line)|code-block|syntax|javascript|1336315|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I think you want to do this instead:

<pre><code>from __future__ import with_statement

with open("out.txt","wt") as file_out:
 with open("in.txt") as file_in:
 for line in file_in:
 file_out.write(line)
</code></pre>

blocks|key|1551968|text|这在Python+3+since+v3.1和Python+2.7中是可能的。新的with+syntax支持多个上下文管理器：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1551969|with+A()+as+a,+B()+as+b,+C()+as+c:
++++doSomething(a,b,c)|code-block|syntax|javascript|1551970|与contextlib.nested不同的是，这保证了a和b将调用它们的__exit__()，即使C()或它的__enter__()方法引发异常。|1551971|您还可以在以后的定义中使用较早的变量(下面的h/t+Ahmad+)：|1551972|with+A()+as+a,+B(a)+as+b,+C(a,+b)+as+c:
++++doSomething(a,+c)|1551973|从Python3.10开始，you+can+use+parentheses|1551974|with+(
++++A()+as+a,+
++++B(a)+as+b,+
++++C(a,+b)+as+c,
):
++++doSomething(a,+c)|1551975|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/3.1/reference/compound_stmts.html#with|1|http://docs.python.org/dev/whatsnew/2.7.html#other-language-changes|2|https://docs.python.org/3/reference/compound_stmts.html#the-with-statement|3|https://stackoverflow.com/questions/893333/multiple-variables-in-a-with-statement#comment78254813_1073814|4|https://docs.python.org/3/whatsnew/3.10.html#parenthesized-context-managers^0|14|4|2|J|0|M|A|1|14|B|2|0|0|1|H|R|1|T|1|10|A|1D|3|1J|B|0|Q|5|3|0|0|E|N|4|0|0^^$0|@$1|2|3|4|5|6|7|1A|8|@$9|1B|A|1C|B|C]]|D|@$9|1D|A|1E|1|1F]|$9|1G|A|1H|1|1I]|$9|1J|A|1K|1|1L]]|E|$]]|$1|F|3|G|5|H|7|1M|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1N|8|@$9|1O|A|1P|B|C]|$9|1Q|A|1R|B|C]|$9|1S|A|1T|B|C]|$9|1U|A|1V|B|C]|$9|1W|A|1X|B|C]|$9|1Y|A|1Z|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|20|8|@]|D|@$9|21|A|22|1|23]]|E|$]]|$1|O|3|P|5|H|7|24|8|@]|D|@]|E|$I|J]]|$1|Q|3|R|5|6|7|25|8|@]|D|@$9|26|A|27|1|28]]|E|$]]|$1|S|3|T|5|H|7|29|8|@]|D|@]|E|$I|J]]|$1|U|3|-4|5|6|7|2A|8|@]|D|@]|E|$]]]|V|$W|$5|X|Y|Z|E|$10|11]]|12|$5|X|Y|Z|E|$10|13]]|14|$5|X|Y|Z|E|$10|15]]|16|$5|X|Y|Z|E|$10|17]]|18|$5|X|Y|Z|E|$10|19]]]]

It is possible in <a href="http://docs.python.org/3.1/reference/compound_stmts.html#with" rel="noreferrer">Python 3 since v3.1</a> and <a href="http://docs.python.org/dev/whatsnew/2.7.html#other-language-changes" rel="noreferrer">Python 2.7</a>. The new <a href="https://docs.python.org/3/reference/compound_stmts.html#the-with-statement" rel="noreferrer"><code>with</code> syntax</a> supports multiple context managers:
<pre><code>with A() as a, B() as b, C() as c:
 doSomething(a,b,c)
</code></pre>
Unlike the <code>contextlib.nested</code>, this guarantees that <code>a</code> and <code>b</code> will have their <code>__exit__()</code>'s called even if <code>C()</code> or it's <code>__enter__()</code> method raises an exception.
You can also use earlier variables in later definitions (h/t <a href="https://stackoverflow.com/questions/893333/multiple-variables-in-a-with-statement#comment78254813_1073814">Ahmad</a> below):
<pre><code>with A() as a, B(a) as b, C(a, b) as c:
 doSomething(a, c)
</code></pre>
As of Python 3.10, <a href="https://docs.python.org/3/whatsnew/3.10.html#parenthesized-context-managers" rel="noreferrer">you can use parentheses</a>:
<pre><code>with (
 A() as a, 
 B(a) as b, 
 C(a, b) as c,
):
 doSomething(a, c)
</code></pre>

blocks|key|1336450|text|在Python+3.1%2B中，您可以指定多个上下文表达式，并且将像嵌套多个with语句一样处理这些表达式：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1336451|with+A()+as+a,+B()+as+b:
++++suite|code-block|syntax|javascript|1336452|等同于|1336453|with+A()+as+a:
++++with+B()+as+b:
++++++++suite|1336454|这也意味着您可以在第二个表达式中使用第一个表达式中的别名(在处理数据库连接/游标时很有用)：|1336455|with+get_conn()+as+conn,+conn.cursor()+as+cursor:
++++cursor.execute(sql)|1336456|entityMap^0|10|4|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|10|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|T|$]]

In Python 3.1+ you can specify multiple context expressions, and they will be processed as if multiple <code>with</code> statements were nested:

<pre><code>with A() as a, B() as b:
 suite
</code></pre>

is equivalent to

<pre><code>with A() as a:
 with B() as b:
 suite
</code></pre>

This also means that you can use the alias from the first expression in the second (useful when working with db connections/cursors):

<pre><code>with get_conn() as conn, conn.cursor() as cursor:
 cursor.execute(sql)
</code></pre>

blocks|key|1336470|text|从Python3.10开始，Parenthesized+context+managers有了一个新特性，它支持如下语法：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1336471|with+(
++++A()+as+a,
++++B()+as+b
):
++++do_something(a,+b)|code-block|syntax|javascript|1336472|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.python.org/3.10/whatsnew/3.10.html#parenthesized-context-managers^0|E|U|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

From Python 3.10 there is a new feature of <a href="https://docs.python.org/3.10/whatsnew/3.10.html#parenthesized-context-managers" rel="noreferrer">Parenthesized context managers</a>, which permits syntax such as:
<pre><code>with (
 A() as a,
 B() as b
):
 do_something(a, b)
</code></pre>

Is it possible to declare more than one variable using a <code>with</code> statement in Python?

Something like:

<pre><code>from __future__ import with_statement

with open("out.txt","wt"), open("in.txt") as file_out, file_in:
 for line in file_in:
 file_out.write(line)
</code></pre>

... or is cleaning up two resources at the same time the problem?

Multiple variables in a 'with' statement?

数据库

Python

是否可以在Python语言中使用with语句声明多个变量？类似于：from __future__ import with_statementwith open("out.txt","wt"), open("in.txt") as file_out, file_in:    for line in file_in:   ...

问在“with”语句中有多个变量？
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问在“with”语句中有多个变量？
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