blocks|key|152575|text|我只能猜测您正在寻找pass语句，有时需要创建一个空代码块以防止语法错误。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|152576|if+mostlyhappencondition:
++++pass
else:
++++do_something()|code-block|syntax|javascript|152577|更常见的做法是这样做，这在逻辑上是等效的：|152578|if+not+mostlyhappencondition:
++++do_something()|152579|这里没有显著的性能提升。|152580|entityMap^0|A|4|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|Y|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|R|$]]

I can only guess you're looking for the <code>pass</code> statement, sometimes needed to create an empty code block to prevent a syntax error.

<pre><code>if mostlyhappencondition:
 pass
else:
 do_something()
</code></pre>

It would be much more usual to just do this, which is logically equivalent:

<pre><code>if not mostlyhappencondition:
 do_something()
</code></pre>

There are no significant performance gains to be found here.

blocks|key|370859|text|直到你在if+True:中没有任何你能做的事情|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|370860|if+not+mostlyhappenedcondition:
+++do+something()|code-block|syntax|javascript|370861|如果你不需要在"+If“中放任何东西，那么它在你的代码中就是多余的。|370862|entityMap^0|4|8|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

Till the time you dont have any thing in <code>if True:</code> you could do

<pre><code>if not mostlyhappenedcondition:
 do something()
</code></pre>

If you dont have to put any thing in "if" even in future, then it is redundunt in your code.

blocks|key|152641|text|如果"+if“中没有else用例，则性能会有所提高，因为字节码不会将执行传递到"if”用例中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|152642|下面是一些函数和dis.dis(foo)的输出|offset|length|style|CODE|152643|以下示例应用程序：|152644|def+foo(x):
++++if+x:
++++++++pass
++++else:
++++++++return+x%2B2|code-block|syntax|javascript|152645|反汇编为：|152646|5+++++++++++0+LOAD_FAST++++++++++++++++0+(x)
++++++++++++3+POP_JUMP_IF_FALSE++++++++9

6+++++++++++6+JUMP_FORWARD+++++++++++++8+(to+17)

8+++++>>++++9+LOAD_FAST++++++++++++++++0+(x)
+++++++++++12+LOAD_CONST+++++++++++++++1+(2)
+++++++++++15+BINARY_ADD++++++++++
+++++++++++16+RETURN_VALUE++++++++
++++++>>+++17+LOAD_CONST+++++++++++++++0+(None)
+++++++++++20+RETURN_VALUE++++++++|152647|以下是|152648|def+foo(x):
++++if+not+x:
++++++++return+x%2B2|152649|152650|11+++++++++++0+LOAD_FAST++++++++++++++++0+(x)
+++++++++++++3+POP_JUMP_IF_TRUE++++++++14

12+++++++++++6+LOAD_FAST++++++++++++++++0+(x)
+++++++++++++9+LOAD_CONST+++++++++++++++1+(2)
++++++++++++12+BINARY_ADD++++++++++
++++++++++++13+RETURN_VALUE++++++++
+++++++>>+++14+LOAD_CONST+++++++++++++++0+(None)|152651|entityMap^0|0|8|C|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|12|8|@$D|13|E|14|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|15|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|16|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|17|8|@]|9|@]|A|$]]|$1|Q|3|R|5|L|7|18|8|@]|9|@]|A|$M|N]]|$1|S|3|T|5|6|7|19|8|@]|9|@]|A|$]]|$1|U|3|V|5|L|7|1A|8|@]|9|@]|A|$M|N]]|$1|W|3|P|5|6|7|1B|8|@]|9|@]|A|$]]|$1|X|3|Y|5|L|7|1C|8|@]|9|@]|A|$M|N]]|$1|Z|3|-4|5|6|7|1D|8|@]|9|@]|A|$]]]|10|$]]

There is a performance improvement if there isn't an else case in the "if", since the bytecodes don't pass execution into the "if" case. 

Here's some functions and the output of <code>dis.dis(foo)</code>

The following sample app: 

<pre><code>def foo(x):
 if x:
 pass
 else:
 return x+2
</code></pre>

Disassembles to:

<pre><code>5 0 LOAD_FAST 0 (x)
 3 POP_JUMP_IF_FALSE 9

6 6 JUMP_FORWARD 8 (to 17)

8 &gt;&gt; 9 LOAD_FAST 0 (x)
 12 LOAD_CONST 1 (2)
 15 BINARY_ADD 
 16 RETURN_VALUE 
 &gt;&gt; 17 LOAD_CONST 0 (None)
 20 RETURN_VALUE 
</code></pre>

The following

<pre><code>def foo(x):
 if not x:
 return x+2
</code></pre>

Disassembles to:

<pre><code>11 0 LOAD_FAST 0 (x)
 3 POP_JUMP_IF_TRUE 14

12 6 LOAD_FAST 0 (x)
 9 LOAD_CONST 1 (2)
 12 BINARY_ADD 
 13 RETURN_VALUE 
 &gt;&gt; 14 LOAD_CONST 0 (None)
</code></pre>

It's very common in C: hacking 'empty if statement' like this:

<pre><code>if(mostlyhappencondition)
 ;#empty statement
else{
 dosomething;
}
</code></pre>

It's working in Python? I mean, can we improve the app's performance by using that? I'd also like to know why.

How to create an 'empty if statement' in python

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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这在C中很常见:像这样破解'empty if语句‘：if(mostlyhappencondition)    ;#empty statementelse{    dosomething;}它能在Python中工作吗？我的意思是，我们可以通过使用它来提高应用程序的性能吗？我也想知道为什么。

问如何在python中创建“空if语句”
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