blocks|key|3578967|text|typ,+dat是一个元组。当在赋值a,+b+=+x的左侧使用时，它等同于：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3578968|a+=+x[0]
b+=+x[1]|code-block|syntax|javascript|3578969|在您的示例中，typ,+dat+=+imap_conn.search(None,+search_string)等同于：|3578970|search_res+=+imap_conn.search(None,+search_string)
typ+=+search_res[0]
dat+=+search_res[1]|3578971|这种在赋值的左侧编写元组的技术称为元组解包。|3578972|entityMap^0|0|8|I|8|0|0|7|1C|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|12|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|R|$]]

<code>typ, dat</code> is a tuple. When used on the left hand side of an assignment <code>a, b = x</code> it is equivalent to:

<pre><code>a = x[0]
b = x[1]
</code></pre>

In your example, <code>typ, dat = imap_conn.search(None, search_string)</code> is equivalent to:

<pre><code>search_res = imap_conn.search(None, search_string)
typ = search_res[0]
dat = search_res[1]
</code></pre>

This technique of writing a tuple on the left hand side of an assignment is known as tuple unpacking.

blocks|key|3864291|text|它是元组解包，参见Python+documentation。如果您的函数返回一个元组，您总是可以使用类似于a,+b+=+func()的语法对其进行解包。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3864292|此外，您还可以动态使用元组，比如a,+b+=+b,+a可以用来交换两个值。|3864293|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/tutorial/datastructures.html#tuples-and-sequences^0|1H|D|9|K|0|0|G|B|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@$9|S|A|T|1|U]]|E|$]]|$1|F|3|G|5|6|7|V|8|@$9|W|A|X|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]]]

It is tuple unpacking, see <a href="http://docs.python.org/tutorial/datastructures.html#tuples-and-sequences" rel="nofollow">Python documentation</a>. If your function returns a tuple you can always unpack it using a syntax similar to <code>a, b = func()</code>.

Also, you can use tuples on the fly, like <code>a, b = b, a</code> can be used for swapping two values.

blocks|key|214197|text|typ,+dat+=+imap_conn.search(None,+search_string)|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|214198|右侧的表达式返回两个赋值给左侧的两个变量的值。|unstyled|214199|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>typ, dat = imap_conn.search(None, search_string)
</code></pre>

The expression on right-hand side returns two values which are assigned to the two variables on the left-hand side.

blocks|key|3579083|text|取决于搜索返回的内容。可以使用该语法对结果进行解包。举个例子：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3579084|>>>x,+y+=+(1,2)
>>>x
1
>>>y
2
>>>+x,+y+=[(1,2),+[1,2,3,(1,2)]]
>>>+x
(1,+2)
>>>+y
[1,+2,+3,+(1,+2)]|code-block|syntax|javascript|3579085|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|$]]

Depends what search is returning. You can unpack a result using that syntax. So for example:

<pre><code>&gt;&gt;&gt;x, y = (1,2)
&gt;&gt;&gt;x
1
&gt;&gt;&gt;y
2
&gt;&gt;&gt; x, y =[(1,2), [1,2,3,(1,2)]]
&gt;&gt;&gt; x
(1, 2)
&gt;&gt;&gt; y
[1, 2, 3, (1, 2)]
</code></pre>

blocks|key|3579132|text|在Python中，您可以按照以下代码分配和/或返回多个值：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3579133|def+fn+():
++++return+(7,+2)

(seven,+two)+=+fn()
print+seven
print+two
print+fn()|code-block|syntax|javascript|3579134|这将输出以下内容：|3579135|7
2
(7,+2)|3579136|我自己更喜欢显式的元组语法(带括号的语法)，因为我认为它使意图更清晰。|3579137|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

In Python, you can assign and/or return more than one value, as per the following code:

<pre><code>def fn ():
 return (7, 2)

(seven, two) = fn()
print seven
print two
print fn()
</code></pre>

This outputs:

<pre><code>7
2
(7, 2)
</code></pre>

I prefer the explicit tuple syntax (the one with the parentheses) myself since I believe it makes the intent clearer.

blocks|key|3864490|text|这就是所谓的“解包”，我相信imap_conn.search(None,+search_string方法返回2个值(可能是一个元组)，这种表示法允许你一次将它们赋给2个变量。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3864491|这相当于：|3864492|return_val+=+imap_conn.search(None,+search_string)
typ+=+return_val[0]
dat+=+return_val[1]|code-block|syntax|javascript|3864493|entityMap^0|E|10|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|S|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

This is what is called "unpacking", i believe the <code>imap_conn.search(None, search_string</code> method returns 2 values (probably a tuple), this notation allows you can assign them to 2 variables in one shot.

This is equivalent to:

<pre><code>return_val = imap_conn.search(None, search_string)
typ = return_val[0]
dat = return_val[1]
</code></pre>

blocks|key|3864517|text|赋值的语法在http://docs.python.org/reference/simple_stmts.html#assignment-statements中给出|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3864518|assignment_stmt+::=++(target_list+"=")%2B+(expression_list+%7C+yield_expression)
target_list+++++::=++target+(","+target)*+[","]
target++++++++++::=++identifier
+++++++++++++++++++++%7C+"("+target_list+")"
+++++++++++++++++++++%7C+"["+target_list+"]"
+++++++++++++++++++++%7C+attributeref
+++++++++++++++++++++%7C+subscription
+++++++++++++++++++++%7C+slicing|code-block|syntax|javascript|3864519|赋值的左侧包含一个或多个逗号分隔的target_list。然后将右侧的序列解压到每个目标中。请注意，该定义是递归的，因此您甚至可以执行以下操作：|style|CODE|3864520|a,+[b,+c,+[d,+e]],+f+=+1,+(2,+3,+(4,+5)),+6|3864521|但在每个级别上，元素的数量和嵌套必须匹配。如果您使用的是Python3，那么有一个在target_list中包含*target的选项，它将接受数量可变的参数。|3864522|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/reference/simple_stmts.html#assignment-statements^0|6|20|0|0|0|H|B|0|0|1K|7|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|F|7|12|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|13|8|@$A|14|B|15|K|L]]|9|@]|C|$]]|$1|M|3|N|5|F|7|16|8|@]|9|@]|C|$G|H]]|$1|O|3|P|5|6|7|17|8|@$A|18|B|19|K|L]]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]]]

The syntax for assignments is given at <a href="http://docs.python.org/reference/simple_stmts.html#assignment-statements" rel="nofollow">http://docs.python.org/reference/simple_stmts.html#assignment-statements</a>

<pre><code>assignment_stmt ::= (target_list "=")+ (expression_list | yield_expression)
target_list ::= target ("," target)* [","]
target ::= identifier
 | "(" target_list ")"
 | "[" target_list "]"
 | attributeref
 | subscription
 | slicing
</code></pre>

the left hand side of the assignment contains one or more <code>target_list</code> which are comma separate targets. A sequence on the right hand side is then unpacked into each target. Notice that the definition is recursive, so you can even do things like:

<pre><code>a, [b, c, [d, e]], f = 1, (2, 3, (4, 5)), 6
</code></pre>

but at each level the number of elements and the nesting must match. If you are using Python 3 then there is an option to include <code>*target</code> in the target_list and that will swallow a variable number of arguments.

I came across this piece of code and am wondering what it means:

<pre><code>typ, dat = imap_conn.search(None, search_string)
</code></pre>

What exactly does the <code>typ, dat</code> part of the line mean?

Python variable declarations

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我偶然发现了这段代码，我想知道它是什么意思：typ, dat = imap_conn.search(None, search_string)这一行的typ, dat部分到底是什么意思？

问Python变量声明
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